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THE 

SOURCES    AND   MODES 

OF 

INFECTION 


By 


CHARLES    V.    CHAPIN,    M.D.,    Sc.  D. 

SUPERINTENDENT   OP   HEALTH,    PROVIDENCE,    R.  I. 
AUTHOR    OF    "municipal  SANITATION   IN  THE   UNITED  STATES" 


FIRST  EDITION 

FIRST    THOUSAND 


NEW  YORK 

JOHN  WILEY  &  SONS 
Lokdon:    chapman   &   HALL,  Limited 

1910 


Copyright,  1910, 
By  CHARLES  V.  CHAPIN 


Stanbopc  ipress 

p.    H.    CILSON     COMPAMT 
BOSTON,     U.S.A. 


PREFACE. 


This  volume  is  intended  to  indicate  the  principles  which 
should  guide  sanitary  practice,  and  to  show  how  recent  labo- 
ratory work  and  the  epidemiological  study  of  disease  have 
modified  these  principles.  When  I  began  work  as  health  ofl&- 
cer  in  1884  the  filth  theory  was  still  in  favor,  and  it  was 
generally  believed  that  the  germs  of  disease  commonly  grew 
in  decaying  organic  matter.  Yet  contagion  was  recognized 
as  an  important  factor  in  the  spread  of  disease,  and  the  isola- 
tion of  the  sick  was  more  and  more  insisted  upon.  Fifteen 
years  ago  probably  most  health  officials  beheved  that  the 
contagious  diseases  could  be  completely  stamped  out  if  only 
all  persons  sick  with  them  could  be  isolated.  The  air  was 
thought  to  be  the  chief  medium  for  their  transmission,  and 
fomites  the  mechanism  for  their  passage  from  place  to  place. 
Sanitary  practice  was  based  on  these  premises. 

My  own  views  concerning  these  matters  became  greatly 
modified  year  by  year,  partly  owing  to  the  rapidly  accumu- 
lating knowledge  of  bacteria  and  other  disease-producing 
organisms,  and  partly  owing  to  direct  observations  on  the 
manner  in  which  the  infectious  diseases  are  disseminated,  and 
on  the  effect  of  preventive  measures. 

It  now  appears  that  the  growth  of  disease  germs  outside  of 
the  body  is  not  frequent  enough  to  be  an  important  factor  in 
the  causation  of  disease,  but  their  growth  in  the  body  with- 
out causing  sickness,  their  latency  as  it  were,  often  for  many 
months,  is  a  factor  of  very  great  significance.  We  know  now 
that  direct  contact  with  the  sick,  or  with  healthy  carriers  of 
disease  germs,  is  an  exceedingly  frequent  mode  of  transmis- 
sion, and  that  infection  by  means  of  the  air,  or  from  infected 
articles,  is  not  nearly  as  common  as  was  formerly  believed. 

iU 


IV  PREFACE 

We  are  now  better  able  than  ever  before  to  attribute  to  water 
and  milk  their  proper  share  in  the  distribution  of  infection. 
The  recent  discovery  of  the  transmission  of  disease  by  insects 
gives  us  entirely  new  and  most  effective  means  of  combating 
disease.  It  is  time  that  sanitary  measures  directed  against 
the  infectious  diseases  should  be  modified  to  correspond  with 
existing  knowledge.  Present-day  theories  and  present-day 
practice  are  maintained  largely  by  tradition,  and  to  facilitate 
the  adaptation  of  practice  to  the  facts  as  we  now  know  them, 
is  the  purpose  of  this  book.  Some  modifications  of  sanitary 
practice  are  suggested,  but  no  attempt  is  made  to  discuss 
details;  rather  are  general  principles  presented,  which  it  is 
believed  ought  to  guide  administrators  in  their  work. 

While  some  of  the  following  pages  may  seem  rather  radical 
to  many,  I  believe  that  practically  all  laboratory  workers  will 
agree  with  the  contents  of  the  first  chapter,  and  that  a  large 
number  of  bacteriologists  and  health  officers  are  convinced  of 
the  great  importance  of  "  carriers  "  and  mild  unrecognized 
cases.  The  tendency  among  many,  too,  is  to  lay  less  emphasis 
on  infection  by  fomites,  though  perhaps  few  are  ready  to 
give  up  routine  terminal  disinfection  for  the  common  infec- 
tious diseases.  So  also  there  are  very  many  careful  observers 
who  are  attributing  more  and  more  importance  to  what  is 
generally  called  contact  infection. 

The  public  health  administrator  is  placed  at  great  disad- 
vantage because  he  is  obliged  to  base  his  acts  on  knowledge 
which  is  far  from  exact.  The  laboratory  workers  have  accu- 
mulated a  vast  mass  of  quite  exact  data  in  regard  to  the  caus- 
ative relation  of  bacteria  and  protozoa  to  disease,  and  no  one 
appreciates  this  more  than  the  writer,  but  there  are  many 
problems  which  the  laboratory  men  cannot  solve,  and  many 
others  which  they  have  failed  to  solve.  The  epidemiologist 
must  study  in  the  field  the  way  in  which  disease  is  caused. 
He  must  use  the  statistical  method,  and  the  application  of 
statistical  methods  to  epidemiology  is  more  difficult  and  less 
attractive  than  laboratory  experiment. 


PREFACE  V 

We  need  to  measure  more  carefully  the  relative  Importance 
of  different  sources  of  disease  and  different  modes  of  infec- 
tion. It  is  not  so  important  to  know  that  typhoid  bacilli 
live  in  water  for  weeks,  as  it  is  to  know  that  99  per  cent  die 
in  one  week.  It  is  not  enough  to  discover  that  diphtheria 
bacilli  can  be  recovered  from  articles  in  the  sick-room;  we 
must  learn  how  often  they  are  found  and  how  often  disease 
is  traced  to  such  a  source.  We  have  for  years  been  much 
alarmed  because  tubercle  bacilli  are  found  in  milk,  but  since 
a  serious  effort  has  been  made  to  measure  the  actual  danger, 
the  alarm  has  greatly  diminished.  Doubtless  the  house  fly 
has  been  the  cause  of  typhoid  fever,  but  in  what  percentage 
of  cases  we  are  profoundly  ignorant.  Healthy  carriers  of 
diphtheria  have  certainly  transmitted  the  disease  to  others, 
and  we  should  earnestly  try'  to  determine  the  amount  of 
diphtheria  caused  in  this  way.  The  attempt  is  made  in  the 
following  pages  to  estimate  roughly,  with  the  very  imperfect 
material  now  available,  the  relative  importance  of  different 
factors  in  the  extension  of  infectious  diseases.  The  conclu- 
sions must  to  a  large  extent  be  merely  tentative,  and  as 
indicating  lines  for  further  study. 

I  am  under  great  obligations  to  my  friends  Dr.  H.  W.  Hill 
and  particularly  Prof.  F.  P.  Gorham  for  many  suggestions 
and  criticisms,  but  neither  is  to  be  considered  at  all 
responsible  for  any  of  the  views  presented. 

The  book  is  intended  primarily  for  health  officers  and  phy- 
sicians, but  it  is  hoped  that  many  others  will  find  some  parts 
interesting  and  suggestive. 

CHARLES    V.  CHAPIN. 
Providence,  April,  1910. 


CONTENTS. 


CHAPTER  I. 

LIFE   OF   DISEASE    GERMS   OUTSIDE   OF   THE   BODT. 

Review  of  evidence  of  growth  of  disease  germs  outside  the  body, 
anthrax,  black  leg,  tetanus.  —  Typhoid  bacilli  in  soil,  water,  ice, 
milk.  —  Epidemiological  evidence  relating  to  typhoid  fever.  —  Evi- 
dence relating  to  cholera,  Mediterranean  fever,  plague,  dysentery, 
bacteria  of  suppuration,  diphtheria  and  various  other  diseases.  — 
Reasons  for  former  belief  in  "filth  theory"  of  disease.  —  Epidemio- 
logical evidence  against  soil  infection.  —  Conclusions.  —  Relations  of 
these  views  to  public  sanitation. 

CHAPTER  II. 

CARRIERS   AND   MISSED   CASES. 

Importance  of  the  subject.  —  Evidence  of  the  occurrence  of  carriers 
and  missed  cases,  and  reference  to  disease  caused  by  them  in  typhoid 
fever,  cholera,  dysentery,  cerebro-spinal  meningitis,  diphtheria,  glan- 
ders, influenza,  pneumonia,  gonorrhea,  tuberculosis,  leprosy,  suppura- 
tion, tetanus,  scarlet  fever,  smallpo.x,  measles,  protozoan  diseases,  such 
as  cattle  fever,  malaria,  sleeping  sickness,  nagana,  syphilis,  amebic 
dysentery  and  yellow  fever.  —  Conclusions. 

CHAPTER   III. 

LIMITATIONS  TO   THE    VALUE   OF   ISOLATION. 

The  number  of  carriers  and  mi.sscd  cases.  —  Not  realized  by  health 
officials.  —  Failure  of  isolation  in  Providence.  —  Ho.spitalization  has 
not  materially  lessened  infectious  disease.  —  Less  isolation  followed  by 
less  diphtheria  in  Providence. —  Failure  of  isolation  in  institutions. — 
Failures  in  the  isolation  of  measles,  of  cerebro-spinal  meningitis,  of 
smallpox.  —  Failure  due  to  carriers  and  mis.sed  cases.  —  Difficulties  in 
the  i.solati()n  of  diiihtlieria.  —  .Vb.solute  isolation  not  possil)le.  —  Mod- 
erate isolation  sufficient.  —  Infection  not  so  easy  as  was  believed. — 
Isolation  effective  at  the  beginning  of  an  outbreak,  rarely  later.  —  The 
more  carriers  the  le.s.s  effective  is  isolation.  —  True  value  of  isolation 
hospitals.  —  Details  of  home  isolation.  —  Summary. 


Vm  CONTENTS 

CHAPTER  IV. 

INFECTION    BY    CONTACT. 

Transmission  of  gonorrhea  by  indirect  contact.  —  Of  syphilis  in  the 
same  way.  —  Typhoid  fever  spread  by  contact.  —  Reasons  why  contact 
infection  has  been  disregarded.  —  Mode  of  contact  infection  in  typhoid 
fever.  —  Contact  infection  in  dysentery.  —  Cholera.  —  Anchylostomi- 
asis.  —  Gonorrhea.  —  Transfer  of  nasal  and  oral  secretions  by  contact. 
— Presence  of  germs  in  secretions  and  on  various  objects. — Diseases  do 
not  spread  from  family  to  family  in  tenements.  —  No  cross  infection 
in  hospitals  except  by  contact.  —  Contact  infection  in  tuberculosis.  — 
Protection  from  contact  infection  a  personal  matter.  —  Need  for  urging 
personal  cleanliness. 

CHAPTER  V. 

INFECTION    BY   FOMITES. 

Definition.  —  Fomites  and  yellow  fever.  —  Examples  of  alleged 
fomites  infection.  —  Infection  by  clothing,  rooms,  rags,  money.  —  Fomites 
infection  in  tetanus,  anthrax,  typhoid  fever,  diphtheria,  plague.  —  No 
evidence  that  fomites  are  of  much  importance.  —  Reasons  for  belief  in 
fomites.  —  Effect  of  drying  on  bacteria  of  different  kinds.  —  The  find- 
ing of  bacteria  on  fomites.  —  Drying  of  vaccine  and  smallpox  virus.  — 
Summary  of  bacteriological  evidence.  —  Experimental  work  with  yellow 
fever,  plague.  —  Results  of  abandoning  disinfection  in  Providence.  — 
Disinfection  in  other  diseases.  —  Conclusions. 

CHAPTER  VI. 

INFECTION    BY    AIR. 

Alleged  aerial  transmission  of  smallpox,  scarlet  fever,  diphtheria, 
typhoid  fever,  influenza,  measles.  —  History  of  surgical  technique  shows 
that  air-borne  infection  is  of  little  moment.  —  Air-borne  anthrax.  — 
Bacteria  not  given  off  from  moist  surfaces.  —  Bacteria  carried  in  dust.  — 
Dust  and  the  germs  of  typhoid  fever,  diphtheria,  plague.  —  Dust  and 
tubercle  bacilH.  —  Finding  of  tubercle  bacilli  in  dust.  —  Other  bacteria 
in  dust.  —  Droplet  infection.  —  Finding  of  bacteria  in  air.  —  Experi- 
mental work  with  tuberculosis,  Mediterranean  fever,  anthrax,  plague.  — 
Conclusions. 

CHAPTER  VII. 

INFECTION    BY   FOOD    AND    DRINK. 

The  Broad  Street  well.  —  North  Boston  well.  —  Typhoid  fever  due 
to  water.  —  Cholera,  dysentery,  diarrhea,  malaria  and  yellow  fever.  — 
Purification  of  water.  —  Ice.  —  Milk,  number  of  outbreaks.  —  Mode 


CONTENTS  IX 

of  infection  of  the  milk.  —  Tuberculosis  and  milk,  evidence  of  infec- 
tion. —  Bacilli  in  market  milk.  —  Amount  of  tuberculosis  due  to  milk. 

—  Mediterranean    fever,  anthrax,  foot-and-mouth    disease,  rabies.  — 
Diarrhea.  —  Infection  by  meat.  —  Infection  by  shellfish.  —  Crawfish. 

—  Watercress.  —  Celery. 

CHAPTER   VIII. 

INFECTION   BY   INSECTS. 

Insects  as  biological  and  as  mechanical  carriers.  —  Pioneer  work  of 
Smith  and  Kilborne  in  cattle  fever. — Malaria. — Modes  of  control  .quinia, 
isolation,  screening;  mosquito  reduction;  practical  results. — Yellow 
fever  carried  by  mosquitoes,  not  by  fomites.  —  Control  of  yellow 
fever;  quarantine,  isolation;  mosquito  control;  practical  results.  — 
Filariasis,  sleeping  sickness,  kala-azar,  dengue,  relapsing  fever,  Rocky 
Mountain  fever.  —  Bubonic  plague  and  fleas.  —  Anthrax.  —  Carriage 
of  bacteria  on  the  bodies  of  insects.  —  Flies  as  carriers  of  disease,  of 
cholera,  dysentery  and  diarrhea.  —  Typhoid  fever,  prevailing  views 
as  to  relation  of  flies  to  disease.  —  Statistical  proof.  —  Control  of  fly 
nuisance.  —  Conclusions. 


THE   SOURCES   AND   MODES   OF 
INFECTION. 


CHAPTER  I. 

LIFE   OF    DISEASE   GERMS   OUTSIDE   OF    THE    BODY 

Former  Theories.  —  From  time  immemorial  miasms,  ma- 
larias, vapors  and  emanations,  gaseous  or  otherwise,  have 
been  believed  to  be  the  frequent  cause  of  disease.  These 
miasms  were  thought  to  arise  from  stagnant  marshes,  deci'v- 
ing  vegetation,  putrid  animal  matter,  and  indeed  hlfh 
of  every  kind.  This  belief  in  the  extra-corporal  origin  of 
disease  reached  its  widest  acceptance  about  the  middle  of 
the  nineteenth  century.  The  rise  of  the  germ  theory  greatly 
strengthened  it.  The  discovery  of  bacteria  and  of  their 
wide  distribution  and  almost  universal  growth  in  dead 
organic  substances,  and  the  theory  that  these  bacteria  were 
the  real  cause  of  disease,  led  men  to  look  for  the  source  of 
disease  outside  of  the  body,  and  chiefly  in  dead  animal  and 
vegetable  matter.  With  the  passing  of  the  germ  theory  as 
a  theory,  and  with  the  demonstration  of  the  parasitic  nature 
of  so  many  of  our  most  important  and  dreaded  discast^s,  the 
opportunity  was  afforded  for  studying  in  detail  the  bacteria 
and  protozoa  which  arc  the  specific  causes  of  these  diseases. 
Much  has  been  done  by  laboratory  workers  to  unravel  the 
life  history  of  these  minute  forms,  and  it  is  well  for  us  to 
examine  the  knowledge  thus  gained,  and  also  the  newer 
epidemiological  observations  on  the  spread  of  the  infectious 
diseases,  and  in  the  light  of  these  data  question  the  belief 
that  these  diseases  have  their  origin  in  the  outer  world  rather 

1 


2  THE  SOURCES  AND  MODES  OF  INFECTION 

than  in  the  bodies  of  men  or  animals.    Let  us  consider  some 
of  these  diseases  in  detail. 

Anthrax  is  not  common  in  the  United  States,  but  it  is  of 
much  interest  from  a  scientific  standpoint.  It  was  the  first 
disease  definitely  proved  to  be  caused  by  bacteria.  It  is 
of  particular  interest  in  this  connection  because  a  relation 
to  the  soil  has  been  better  established  for  this  than  for  any 
other  disease.  Practically  all  writers  are  agreed  that  the 
soil  may  become  infected  with  anthrax,  and  remain  so  for 
a  long  time,  and  that  animals  pastured  upon  such  soil  con- 
tract the  disease  by  taking  the  bacteria  in  with  the  food, 
or  inspired  air,  or  through  abrasions  of  the  skin.  That  this 
soil  infection  is  not  the  sole,  or  perhaps  even  the  most  com- 
mon source  of  infection,  and  that  danger  from  this  source 
has  perhaps  been  somewhat  exaggerated,  is  probably  true. 
Thus  Delepine  ^  from  studying  recent  outbreaks  in  Great 
Britain  is  convinced  that  the  disease  is  perpetuated  by 
a  more  or  less  direct  contact,  chiefly  with  unrecognized  or 
concealed  cases,  and  that  there  is  no  necessity  for  supposing 
a  long  continued  soil  infection,  and  no  direct  evidence  for 
it  as  the  principal  source  of  the  disease.  McFadyean  ^  can- 
not trace  anthrax  in  Britain  to  the  soil,  and  thinks  it  im- 
probable that  it  grows  there,  or  it  would  be  more  common. 
Moreover  it  does  not  grow  well  under  60°.  Legge  ^  notes  that 
animal  anthrax  does  not  increase  in  the  summer  as  it  would 
be  likely  to  if  it  were  due  to  growth  in  the  soil.  Moore  *  does 
not  think  the  bacillus  maintains  a  saprophytic  existence. 
In  Louisiana^  the  extensive  outbreak  in  the  latter  years  of 
the  nineteenth  century  was  believed  to  be  due  to  some  extent 
to  food  infection,  and  to  a  large  extent  to  direct  inoculation 

1  Delepine,  Pub.  Health,  1904-5,  XVII,  491. 

2  McFadyean,  J.  Comp.  Path,  and  Therap.,  Edinb.  and  Lond.,  1903, 
XVI,  35. 

'  Legge,  Lancet,  Lond.,  1905,  I,  695. 
*  Rep.  Comm.  of  Agric.  N.  Y.,  1907. 
®  Louisiana  Agricultural  Experiment  Sta.,  Bull.  No.  60,  2d.  s.,  1900. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY        3 

by  a  species  of  horsefly,  Tabanus  lineola.  Outbreaks  of 
anthrax  have  occurred  every  few  years  in  Louisiana  for  over 
half  a  century,  and  persistent  soil  infection  has  been  alleged 
as  theip  source.  Very  likely  it  is  so  to  a  certain  extent,  but 
on  the  other  hand  there  is  no  doubt  that  the  interval  be- 
tween the  outbreaks  may  well  be  bridged  over  by  a  more  or 
less  direct  connection  between  sporadic  and  unrecognized 
cases  occurring  in  the  interval.  That  such  cases  really  occur 
is  shown  by  Delepine's  investigations  of  similar  conditions 
in  England.  Nevertheless  almost  all  veterinary  and  medical 
writers  are  agreed  as  to  the  long  continued  soil  infection  of 
certain  areas.  Evidence  of  this  is  forthcoming  from  France, 
Germany,  England  ^  and  the  United  States.  In  England  such 
infective  areas  are  said  to  be  the  most  numerous  where  refuse 
from  mills  using  foreign  wools  is  used  for  manure.  In  this 
country  anthrax  is  believed  to  have  been  traced  to  morocco 
factories  on  the  Delaware  River  using  large  numbers  of 
foreign  skins. ^  Some  of  the  infected  Delaware  farms  had  new 
tenants  with  new  cattle  each  year,  but  infection  recurred. 
All  the  evidence  pointed  to  persistent  infection  of  the  soil. 
Similarly  infected  farms  or  fields  are  reported  from  New  Jer- 
sey,^ from  the  Genesee  valley  *  and  from  Louisiana.^  Law 
reports  that  200  cases  in  cattle,  and  3  in  human  beings  re- 
sulted in  the  space  of  two  weeks,  from  the  soil  infection  of  a 
limited  area.  Dr.  Leonard  Pearson  wrote  me  that  the  evi- 
dence is  conclusive  that  soil  infection  with  anthrax  has  existed 
in  a  number  of  places  in  Pennsylvania.  Two  instances  have 
recently  been  reported  which  seem  to  show  pretty  conclu- 
sively that  anthrax  bacilli  do  grow  in  small  ponds  under 

'  Poore,  The  P^arth  in  Relation  to  the  Preservation  and  Destruction 
of  Contagia,  Lond.,  1902,  9-21. 

*  Delaware  Agricultural  Experiment  Sta.,  Bull.  No.  32,  1896,  6. 
'  Rep.  St.  Bd.  Health,  N.  J.,  1904,  5. 

<  Law,  Text-Book  of  Veterinary  Medicine,  Ithaca,  1902,  IV,  195. 

*  Louisiana  Agricultural  Experiment  Sta.,  Bull.  No.  60,  2d  e.,  Insert 
opp.  345,  and  357. 


4  THE  SOURCES  AND  MODES  OF  INFECTION 

natural  conditions.  Dr.  J.  Sinclair  Holden,  health  officer  of 
Sudbury,  Co.  Suffolk,  England,  writes  that  in  1905  the  waste 
water  from  a  horsehair  factory  was  discharged  into  a  small 
pond.  There  was  evidently  some  seepage  from  this  pond  to 
another  about  20  feet  distant.  The  second  pond,  in  the  fol- 
lowing year,  was  found  to  be  so  abundantly  filled  with  the 
bacilli  of  anthrax  that  it  seemed  that  there  must  have  been 
free  reproduction.  Hastings  ^  also  reports  that  he  examined 
a  pond  which  had  received  anthrax-infected  tannery  refuse, 
and  that  this  was  teeming  with  the  vegetative  forms  of  the 
bacillus. 

While  there  is  a  good  deal  of  evidence,  apparently  conclu- 
sive, that  soil  may  remain  infected  with  anthrax  for  years, 
there  also  is  evidence  that  the  infection  after  a  time  disap- 
pears. Pasteur  records  instances  of  the  infection  dying  out 
after  a  lapse  of  some  years,^  and  in  Delaware  infection  did 
not  persist  on  all  the  infected  farms. ^  The  fact  that  anthrax 
has  appeared  at  so  many  isolated  points  in  England  and  the 
United  States,  and  though  in  the  majority  of  cases  soil  inocu- 
lation must  have  taken  place,  nevertheless  the  fact  that  the 
disease  has  never  become  widespread  or  long  persistent  locally 
is  sufficient  reason  for  the  conclusion  that  its  virus  does  not, 
in  these  countries  at  least,  find  a  suitable  soil.  If  it  increases 
at  all  in  the  soil  it  is  only  for  a  time,  and  the  tendency  is  for 
it  to  die  out.  In  other  words,  the  history  of  this  disease  is 
best  explained  on  the  hypothesis  that  the  soil  is  infected 
chiefly  if  not  exclusively  by  the  spores,  which  may  retain 
their  virulence  for  years,  but  which  rarely  germinate  in  the 
earth. 

Charbon  S3n3iptomatique.  —  Another  animal  disease  known 
as   black-leg,   or  in    Europe   as   charbon   symptomatique,   is 

'  Hastings,  Paper  read  at  meeting  of  Society  of  American  Bacteri- 
ologists, 1908. 

'  Poore,  The  Earth  in  Relation  to  the  Preservation  and  Destruction 
of  Contagia,  Lond.,  1902,  13. 

^  Delaware  Agricultural  Experiment  Sta.,  Bull.  No.  32,  1896,  7. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY        5 

quite  prevalent  among  cattle  in  this  country.  Like  anthrax 
it  is  caused  by  a  bacillus  that  forms  spores.  Veterinarians 
are  agreed  that  soil  areas  become  infected  with  black-leg  and 
may  remain  so  for  some  time.  Undoubtedly  this  infection 
may  be  explained,  as  is  the  infection  by  anthrax,  as  due  simply 
to  the  resistance  of  the  spores,  and  does  not  necessarily  re- 
quire the  actual  multiplication  of  the  germs  in  the  soil. 

Tetanus  or  lockjaw,  even  before  it  was  known  to  be  due 
to  a  bacillus,  was  believed  to  occur  with  exceptional  fre- 
quency in  limited  areas.  It  has  been  stated  by  numerous 
writers  that  there  is  a  strip  of  land  near  Red  Bank,  New 
Jersey,  where  tetanus  is  decidedly  endemic.  The  disease  was 
also  said  to  be  formerly  extremely  common,  especially 
among  animals,  on  the  eastern  end  of  Long  Island,  but  that 
it  has  now  become  quite  rare  in  that  locahty.  This  alleged 
local  prevalence  on  Long  Island  has  been,  in  this  country  at 
least,  one  of  the  most  frequently  used  arguments  in  sup- 
port of  soil  infection,  but  Overton^  has  shown  that  the 
published  statements  cannot  be  verified,  and  that  the  disease 
has  not  been  especially  prevalent  in  that  locality.  I  have 
corresponded  with  various  officials  in  New  Jersey,  but  have 
never  been  able  to  obtain  any  evidence  of  the  alleged  local 
infection  at  Red  Bank.  Tetanus  is  more  common  in  the 
southern  than  in  the  northern  parts  of  the  United  States, 
and  is  a  very  important  cause  of  death  in  the  West  Indies. 
Before  the  organization  of  the  present  efficient  health  depart- 
ment in  Havana  there  were  often  200  deaths  or  more  annually 
from  infantile  tetanus,  due  to  infection  of  the  navel.  It  has 
long  been  recognized  that  tetanus  follows  wounds  in  which 
dirt  is  forced  deep  into  the  tissues,  and  that  garden  earth  is 
especially  dangerous.  Even  well-established  evidence  of  per- 
sistent local  infection  does  not  prove  growth  in  the  soil.  It 
might  be  due  to  a  great  variety  of  causes. 

Thus  it  has  been  explained  that  the  bacilli  of  tetanus  are 
very  widely  distributed  because  these  bacteria  are  natural 

»  Overton,  Long  Island  M.  J.,  Brooklyn,  1907,  I,  176. 


6  THE  SOURCES  AND  MODES  OF  INFECTION 

inhabitants  of  the  healthy  intestines  of  domestic  animals, 
particularly  the  horse.  Hence  they  are  found  in  profusion 
wherever  the  manure  from  these  animals  falls,  and  soiled  skin 
and  clothing  are  not  likely  to  carry  them.  Theobold  Smith/ 
however,  says  that  there  is  no  evidence  that  the  tetanus 
bacilli  are  normal  inhabitants  of  and  multiply  in  the  intes- 
tines of  animals.  He  inclines  to  the  view  that  their  home  is 
in  the  soil.  Vincent^  after  introducing  tetanus  spores  into 
the  stomach  of  a  rabbit  could  find  no  evidence  of  multipli- 
cation, and  he,  too,  thinks  a  saprophytic  existence  probable. 
The  tetanus  bacillus  forms  spores  which  may  retain  their 
vitality  for  16  years,  so  that  it  is  not  surprising  that  lands 
have  been  known  to  remain  infected  for  several  years. ^  These 
spores,  or  the  bacilli,  are  said  to  have  been  found  in  gelatine,* 
in  blank  cartridges,^  and  on  balls  of  lamp  wick  used  in  Havana 
for  tying  the  umbilical  cord.**  While  the  soil,  and  dirt  gener- 
ally, contain  tetanus  bacilli  or  their  spores,  there  is  no  direct 
evidence  to  show  that  they  are  propagated  outside  of  the  body. 
The  fact  that  they  do  not  grow  in  the  presence  of  air  would 
indicate  that  this  is  not  the  case,  and  the  distribution  of  the 
disease  and  its  comparative  rarity  would  also  lead  to  this 
conclusion.  It  is  not,  of  course,  to  be  denied  that  the  tetanus 
bacillus  may  lead  a  saprophytic  existence.  It  is  very  pos- 
sible that  it  may  do  so,  but  it  certainly  can  be  affirmed  that 
at  present  we  have  no  proof  that  it  does  so,  and  all  observed 
facts  relating  to  the  bacillus,  or  the  disease  caused  by  it,  may 
be  explained  without  assuming  any  such  hypothesis. 

It  is  suggestive  that  the  pathogenic  bacteria  which  are 
oftenest  assumed  to  grow  in  the  soil  are  the  very  ones  the 

*  Theobold  Smith,  J.  Am.  Ass.,  Chicago,  1908,  L,  929. 

^  Vincent,  Compt.  rend.  Soc.  de  biol.  Par.,  1908,  LXV,  12. 

»  Villar,  J.  Comp.  Path,  and  Therap.,  Edinb.  and  Lond.,  1897,  XX. 

*  Tuck,  J.  Path,  and  Bacteriol.  Edinb.  and  Lond.,  1904,  IX,  38. 
'  Dolley,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  466. 

*  Junta  Superior  de  Sanidad  de  la  Isla  de  Cuba,  Suplemento  y  Noto 
Adicional,  1902-3,  4. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY        7 

spores  of  which  may  retain  their  vitahty  for  years.  Is  it  not 
more  Hkelj'  that  it  is  persistence  of  spores,  rather  than  growth 
of  the  bacilU  themselves,  that  in  most  instances  maintains 
the  soil  infection  ? 

Typhoid  Bacilli  in  Soil.  —  It  has  been  amply  demonstrated 
that  water,  milk,  soil  and  various  other  materials  are,  when 
sterile,  suitable  media  for  the  growth  of  the  typhoid  bacillus. 
But  this  fact  is  of  little  practical  importance,  as  sterile  mate- 
rials are  not  ordinarily  found  in  nature,  but  on  the  contrary 
almost  everything  which  could  possibly  be  considered  a  cul- 
ture medium  for  typhoid  and  other  disease  germs  is  swarming 
with  bacteria,  mostly  of  entirely  harmless  varieties.  There 
has  been  much  painstaking  work  to  determine  whether  ty- 
phoid bacilli  actually  do  grow,  or  even  retain  their  vitality, 
in  or  on  a  great  variety  of  substances.  The  difficulties  in 
this  sort  of  experimentation  are  considerable,  and  not  the 
least  is  that  of  picking  out  the  typhoid  bacillus  from  among 
other  forms.  Robertson^  and  Firth  and  Horrocks"  seem  to 
have  made  the  most  elaborate  experiments  in  regard  to  its 
growth  in  soil,  and  to  have  worked  under  more  natural  con- 
ditions than  most  observers.  Robertson  found  that  by 
moistening  soil  from  time  to  time  with  bouillon  he  could 
keep  the  bacillus  alive  for  11  months,  and  even  cause  it  to 
grow.  Firth  and  Horrocks  did  not  find  any  evidence  of 
increase  in  soil  under  a  great  variety  of  conditions.  When 
conditions  were  favorable  it  could  be  recovered  up  to  74  days. 
In  peat  it  could  only  be  recovered  after  13  days.  More 
recently  Mair^  has  been  able  to  recover  the  bacillus  from  un- 
sterilized  soil  in  large  numbers,  for  20  days,  and  in  small 
numbers,  up  to  70  or  80  days.  He  found  no  evidence  of 
increase.  Great  care  was  taken  not  to  introduce  any  nutri- 
tive medium  with  the  bacilli.  Unlike  most  observers,  JMair 
found  that  in  sterile  soil  the  bacilli  disappear  more  rapidly, 

1  Robertson,  Brit.  M.  J.,  Lond.,  1898,  I,  09. 

»  Firth  and  Horrocks,  Brit.  M.  J.,  Lond.,  1902,  II,  936. 

'  Mair,  J.  Ilyg.,  Cambridge,  1908,  VIII,  37. 


8  THE  SOURCES  AND   MODES  OF  INFECTION 

in  11  days  in  fact.  He  believes  that  this  is  due  to  the  chem- 
ical composition  of  the  particular  soil  used.  Smith  ^  working 
with  similar  soil,  unsterilized,  could  not  recover  the  organism 
after  25  days,  and  the  average  duration  in  the  soil  was  15 
days.  Most  observers,  as  Koch,"  Karlinski,^  Uffelmann,^ 
Martin, '"'  Pfuhl  ®  and  others  agree  that  it  does  not  grow  in  soil, 
though  it  may  retain  its  vitality  at  times  for  months.  Savage^ 
found  that  it  died  rapidly  in  tidal  mud,  though  a  few  bacilli 
could  be  recovered  after  five  weeks.  Klein  ^  could  not  find 
the  organism  in  dead  animals  buried  in  earth,  after  20  days, 
but  Loesner  ^  found  it  after  96  days. 

Typhoid  Bacilli  in  Sewage. —  According  to  Park  '°  typhoid 
bacilli  soon  die  out  in  feces,  usually  in  a  few  hours,  but  he 
has  recovered  them  up  to  the  tenth  day.  He  suggested  that 
this  variation  may  depend  on  the  constitution  of  the  feces. 
On  the  other  hand.  Levy  and  Kayser"  note  the  persistence  of 
typhoid  bacilli  in  a  cemented  privy  vault  up  to  5  months 
and  Pfuhl "  recovered  them  after  3  months  from  feces  mixed 
with  garden  earth.  Delepine  ^^  states  that  typhoid  bacilli  will 
survive  in  a  privy  for  a  year.  Rogers*^  found  that  the  bacillus 
lived  only  a  few  days  in  filtered  septic  tank  effluent. 

1  Smith,  Rep.  on  Occurrence  of  Typhoid  Fever  in  Belfast,  1903, 
quoted  by  Mair. 

^  Koch,  Die  Bek  mpfung  des  Typhus,  Berl.,  1903,  14. 
♦  '  Karlinski,  Arch.  f.  Hyg.,  Miinchen  u.  Leipz.,  1891,  XIII,  302. 

*  Uffelmann,  Centralbl.  f.  Bakteriol.  [etc.],  Jena,  1894,  XV,  133. 

'  Martin,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1900-1901,  XXX, 
508. 

*  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  555. 
'  Savage,  J.  Hyg.,  Cambridge,  1905,  V,  146. 

'  Klein,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1898-9,  XXVIII,  363. 

'  Loesner,  Arb.  a.  d.  k.  Gsndhtsamte,  Berl.,  1896,  XII,  448. 

'"  Park,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  852. 

''  Levy  and  Kayser,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena, 
1902,  XXXIII,  489. 

*^  Delepine,  Rep.  Health  of  Manchester,  1907,  82. 

■'  Rogers,  Brit.  M.  J.,  Lond.,  1903,  II,  639. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY         9 

Typhoid  Bacilli  in  Water.  —  Hoffmann '  could  recover  ty- 
phoid germs  from  aquarium  water  after  36  days,  or  from  mud 
after  2  months.  Jordan  and  Russell"  tried  to  imitate  natural 
conditions  by  enclosing  inoculated  water  in  colloidal  sacs  to 
permit  of  osmosis,  and  these  were  placed  in  the  Chicago 
River,  a  sewage-polluted  stream.  They  could  recover  the 
bacilli  for  from  3  to  7  days  only.  Russell  and  Fuller^  repeated 
these  experiments  with  substantially  the  same  results,  though 
they  kept  the  bacillus  alive  in  lake  water  from  8  to  10  days. 
Karlinski^  could  not  recover  typhoid  bacilli  from  water  after' 
6  days,  except  once  in  cistern  water,  where  they  persisted  for 
13  days.  Hewlett^  never  found  them  alive  in  sterilized  Lon- 
don tap  water  over  4  weeks.  Houston  **  has  recently  made 
some  careful  quantitative  studies  of  the  hfe  of  the  typhoid 
bacillus  in  raw  London  tap  water.  In  eighteen  series  of  tests 
the  average  reduction  during  the  first  week  was  99.9  percent, 
but  a  few  could  be  recovered  up  to  the  eighth  week. 

Field '  found  that  typhoid  bacilli  would  survive  in  sea 
water  for  from  6  to  8  days,  but  that  50  percent  died  in  24 
hours. 

Wheeler*  finds  that  in  well  water  with  considerable  pollu- 
tion, at  room  temperature,  and  with  the  exclusion  of  light, 
a  considerable  increase  of  typhoid  organisms  may  take  place. 
Konradi*  also  claims  that  this  bacillus  can  maintain  a  sapro- 
phytic existence  in  water,  but  his  methods  have  been  criti- 
cized, and  in  some  experiments  at  least,  a  good  deal  of  nutrient 

»  Hoffmann,  Arch.  f.  Hyg.,  Miinchen  u.  Leipz.,  1905,  LII,  208. 

*  Jordan  and  Russell,  J.  Infect.  Dis.,  Chicago,  1904,  I,  641. 

»  Russell  and  Fuller,  J.  Infect.  Dis.,  Chicago,  1906  [Suppl.  No.  2],  40. 

*  Karlinski,  Centralbl.  f.  liaktcriol.  (etc.),  Jena,  1889,  VI,  138. 
'  Hewlett,  J.  State  M.,  Lond.,  1905,  XIII,  165. 

"  First  Rep.  on  Research  Work  Metrop.  Water  Bd.,  Lond.,  Abst. 
Pub.  Health  Ix>nd.,  1908,  XXII,  30. 

'  Field,  Rep.  Dept.  Health,  City  of  New  York,  1904,  I,  451. 

"  Wheeler,  J.  Med.  Research,  Best.,  1906,  XV,  269. 

"  Konradi,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena,  1904, 
XXXVI,   203.' 


10  THE  SOURCES  AND   MODES  OF  INFECTION 

material  was  added  to  the  water  with  the  organisms.  The 
report  on  typhoid  fever  in  the  District  of  Columbia^  quotes 
from  Kubler  and  Neufeld,  and  Stroezner  and  Tavel,  instances 
of  alleged  longevity  of  the  typhoid  bacillus  in  well  water  or, 
in  Tavel's  case,  in  tap  water,  but  secondary  contact  infec- 
tion was  not  in  any  instance  absolutely  excluded.  On  the 
other  hand,  the  infection  in  a  reservoir  in  Scranton  was 
proved  to  have  died  out  within  8  weeks.^ 

PfuhP  found  the  bacillus  in  tap  water  after  28  days,  but  not 
after  31  days.  In  artificially  inoculated  seltzer  water  it  lived 
for  27  days.  Hill,^  however,  could  not  recover  it  from  various 
carbonated  "  soft  drinks  "  after  14  hours. 

Typhoid  Bacilli  in  Ice.  —  Various  writers  have  studied  the 
life  of  typhoid  bacilli  in  ice,  and  Prudden,''  Winslow,*^  Park,^ 
Jordan,  Russell  and  Zeit,*  Clark,^  Smith  and  Swingle^"  and 
Wheeler  ^^  have  shown  that  they  tend  to  disappear  gradually, 
somewhat  as  they  do  in  the  water  from  which  the  ice  is 
obtained.  Yet  an  outbreak  is  recorded  caused  by  typhoid 
bacilli  frozen  in  ice  for  eight  months.  But  they  were  in  con- 
siderable masses  of  feces.  ^"  This  is  the  only  reported  outbreak 
in  which  it  is  reasonably  certain  that  infection  was  by  ice. 

Typhoid  and  Oysters.  —  Field  ^^  found  that  in  healthy 
oysters  typhoid  germs  rapidly  died,  and  none  could  be  re- 
covered after  the  ninth  day.    When  the  oysters  were  dead 

1  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull.  No.  35,  178. 

2  N.  York  M.  J.  [etc.],  1907,  LXXXV,  1025. 

»  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  555. 

'  Hill,  Rep.  Bd.  of  Health,  Bost.,  1904,  53. 

^  Prudden,  Med.  Rec,  N.  Y.,  1887,  XXXI,  341. 

«  Winslow,  J.  Mass.  Ass.  of  Bds.  Health,  Bost.,  XI,  133. 

'  Park,  J.  Bost.  Soc.  M.  Sc,  1899-1900,  IV,  213. 

«  Russell  and  Zeit,  J.  Infect.  Dis.,  Chicago,  1904,  I,  660. 

»  Clark,  J.  Mass.  Ass.  Bds.  Health,  Bost.,  XI,  124. 

'"  Smith  and  Swingle,  Science,  N.  Y.,  1905,  n.  s.,  XXI,  481. 

"  Wheeler,  J.  Med.  Research,  Bost.,  1906,  XV,  269. 

'^  Am.  J.  M.  Sc,  Phila.,  1903,  n.  s.,  CXXVI,  680. 

"  Field,  Med.  News,  N.  Y.,  1904,  LXXXV,  571. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      11 

or  djang,  there  was  a  very  considerable  increase.  Klein  ^ 
found  that  in  oysters  kept  in  sea  water  typhoid  bacilli  would 
live  from  6  to  7  days,  but  if  kept  out  of  the  water,  for  11  days. 
In  other  shellfish  their  life  was  longer. 

Typhoid  and  Milk.  —  Sterile  milk  serves  as  an  excellent 
culture  medium  for  the  typhoid  bacillus,  but  ordinary  market 
milk  is  not  favorable  for  its  growth,  owing  to  the  rapid  pro- 
duction of  lactic  acid.  Bassenge "  says  that  when  milk  has 
soured  to  the  extent  of  0.3°-0.4°  Soxhlet,  and  has  continued 
in  this  condition  for  24  hours,  the  bacilli  are  destroyed.  Xeu- 
feld  ^  states  that  they  usually  disappear  from  ordinary  milk 
in  from  2  to  3  days.  Pfuhl  ^  found  the  bacillus  persisting  in 
the  milk  for  13  days.  Rosenau  and  McCoy  have  studied 
this  question  and  reviewed  the  literature."  They  find  that 
raw  milk,  when  first  drawn,  has  a  feeble  antiseptic  action, 
and  typhoid  and  dysenterj^  bacilli,  when  added  to  it,  decrease 
slightly  at  times,  but  within  48  hours  their  numbers  increase 
enormously.  Eyre  ^  also  states  that  the  typhoid  bacillus 
may  increase  in  milk  to  enormous  numbers,  but  as  the 
milk  he  experimented  with  was  drawn  under  careful  aseptic 
precautions,  it  is  quite  likely  that  his  findings  would  not 
obtain  in  ordinary  milk,  owing  to  the  hostile  influence  of 
lactic-acid  and  other  bacteria. 

If  typhoid  bacilli  increase  in  number  in  ordinary  market 
milk,  extensive  outbreaks  ought  to  be  expected  in  our  large 
American  cities,  where  the  milk  is  handled  by  large  dealers 
drawing  their  supply  from  many  producers  situated  at  long 
distances,  so  that  the  milk  is  from  48  to  72  hours  old  before 

'  Klein,  Tr.  Path.  Soc.  Lond.,  190.5,  LVI,  23;  Med.  Press  &  Circ, 
1905,  LXXIX,  264. 

'  Bassenge,  Deutsche  med.  Wchnschr.,  190.3,  XXIX,  67.5,  697. 

>  Ncufeld,  Kollcu.  Wa.ssermann,  Handhuch  [etc.l  Jena,  190.3,  II,  213. 

*  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infection.skrankh.,  Leipz.,  1902,  XL,  555. 

*  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Ilyg.  Lab.  Bull.  No.  41, 
449. 

'  Eyre,  J.  State  M.  Lond.,  1904,  XII,  728. 


12         THE  SOURCES  AND  MODES  OF  INFECTION 

it  reaches  the  consumer.  Any  dilution  ought  to  be  more 
than  balanced  by  the  alleged  increase  in  the  bacteria.  But 
nearly  all  of  the  American  milk  outbreaks  reported  in 
Bulletin  41  of  the  Hygienic  Laboratory  were  on  small 
routes  where  the  interval  between  infection  and  delivery  was 
short.  No  outbreaks  due  to  railroad  milk  were  reported 
from  Boston,  New  York,  Philadelphia,  Chicago,  Buffalo, 
Baltimore,  or  St.  Louis,  and  of  one  hundred  and  twenty- 
nine  outbreaks  in  American  cities  only  two  instances  were 
reported,  namely  in  Washington,  D.  C,  in  which  typhoid 
infection  was  brought  in  over  a  railroad. 

Boers,^  Bruck^  and  PfuhP  have  demonstrated  the  persist- 
ence of  typhoid  bacilli  in  butter  up  to  27  days,  but  few  if 
any  outbreaks  have  been  traced  to  this  article  of  food. 

Mayer*  states  that  paratyphoid  bacilli  will  retain  their 
vitality  in  dried  human  feces  for  a  year  and  a  half. 

No  bacteria  can  grow  except  in  the  presence  of  moisture, 
so  an  increase  of  typhoid  bacilli  on  clothing,  furniture,  wood- 
work, etc.,  is  not  to  be  looked  for.  The  duration  of  life  under 
such  conditions  is  sometimes  shorter  and  sometimes  longer 
than  it  is  in  the  presence  of  moisture.  This  will  be  discussed 
further  in  another  connection. 

It  must  be  confessed  that  the  experimental  evidence  relat- 
ing to  the  growth  and  vitality  of  typhoid  bacilli  outside  the 
body  is  by  no  means  conclusive.  The  evidence  seems  to  be, 
however,  that  they  rarely  if  ever  increase  in  numbers,  and  in 
most  instances  they  tend  to  die  off,  and  that  quite  rapidly, 
often  in  a  few  days,  or  even  hours. 

Epidemiological  Evidence.  Soil.  —  There  is  not  much 
epidemiological  evidence  that  typhoid  bacilli  retain  their 
vitality  outside  of  the  body  for  more  than  a  few  weeks  or 

'  Boers,  cited  in  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg. 
Lab.  Bull.  No.  41,  24. 

^  Bruck,  Deutsche  med.  Wchnschr.,  1903,  XXIX,  460. 

^  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  555. 

*  Mayer,  Miinch.  med.  Wchnschr.,  1908,  LV,  2218. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      13 

perhaps  occasionally  for  a  few  months,  and  there  seems  to 
be  no  such  evidence  of  their  increase,  except  sometimes  in 
milk.  Westcott^  reports  an  instance  where  a  well  continued 
infected  for  20  months.  It  was  claimed  that  the  conditions 
were  such  that  continuous  infection  could  not  have  taken 
place,  but  this  does  not  appear  to  have  been  the  fact. 
The  numerous  instances  given  in  the  Report  on  Typhoid 
Fever  in  the  Spanish  War^  as  showing  the  growth  of  typhoid 
bacilli  in  the  soil,  are  by  no  means  conclusive.  Infected 
soil  was  supposed  to  have  caused  outbreaks  in  various 
army  corps,  but  other  sources  could  not  be  in  any  case 
excluded,  and  the  chances  of  other  modes  of  infection  in 
an  army  are  very  great.  The  infection  was  supposed  to 
have  remained  many  months,  and  it  is  possible  that  it  may 
have  in  some  instances  done  so.  As  a  matter  of  fact  90  per 
cent  of  the  volunteer  regiments  in  the  Spanish  War  sooner 
or  later  became  infected  whether  encamped  on  a  polluted 
site  or  not.  Koch  ^  believed  from  epidemiological  as  well  as 
from  bacteriological  evidence  that  it  is  very  rare  for  an  out- 
break to  be  due  to  long  continued  soil  pollution,  and  that  the 
possibility  of  the  growth  of  the  bacillus  outside  the  body  may 
be  neglected.  In  1902,  Koch  undertook  the  investigation  of 
the  typhoid  fever  which  had  prevailed  for  some  time  in  sev- 
eral villages  in  Trier.  As  a  result  of  his  labors,  every  typhoid 
case  and  typhoid  carrier  in  four  of  the  villages  was  isolated, 
and  the  outbreak  ceased,  showing  that  it  was  due  entirely  to 
contact  infection  and  not  to  soil  infection. 

Epidemiological  Evidence.  Water.  —  Numberless  out- 
breaks of  typhoid  fever  have  been  traced  to  infected  waters. 
In  some  instances  the  pollution  of  rivers  is  continuous,  and 
the  cities  supplied  from  them  suffer  from  a  uniformly  high 

'  Wcstpott,  J.  State  M.  Lond.,  1S90,  VII,  104. 

'  Ahstr.  of  Rep.  on  the  Origin  and  Spread  of  Tj'phoid  Fever  in 
U.  S.  Military  Camps  during  the  Spanish  War  of  1898,  Wash.,  1900, 
20&-209. 

»  Koch,  Die  Bekampfung  dea  Typhus,  Berl.,  1903,  14,  19. 


14  THE  SOURCES  AND   MODES  OF  INFECTION 

death  rate  from  this  disease.  In  most  instances  water  out- 
breaks are  of  an  explosive  character,  the  onset  is  sudden  and 
they  often  end  suddenly,  though  sometimes  the  decline  is 
gradual  owing  to  the  development  of  a  certain  number  of 
secondary  cases  due  to  contact  infection.  A  few  days'  or 
sometimes  a  single  day's  pollution  is  sufficient  to  account 
for  the  whole  outbreak.  Three  outbreaks  of  this  kind  have 
occurred  in  Providence,  and  in  one  instance  it  was  clearly 
traced  to  the  throwing  upon  the  banks  of  the  river  of  the 
excreta  from  an  infected  family.  The  Providence  watershed 
covers  about  ninety-six  square  miles,  and  had  upon  it  in  1900 
a  population  of  some  35,000,  a  large  part  in  villages  along  the 
banks,  but  some  scattered  in  hamlets  and  farms  over  the 
whole  area.  The  death  rate  from  typhoid  fever  in  Rhode 
Island  is  not  less  than  20  per  100,000  in  the  country  districts, 
which  means  seven  deaths  per  annum  on  the  watershed.  As 
the  fatality  is  not  over  10  per  cent,  there  must  be  seventy 
cases,  and  if  we  add  the  "  carriers,"  the  number  of  persons 
each  year  distributing  typhoid  bacilli  on  the  watershed  must 
be  at  least  one  hundred,  and  perhaps  very  much  greater.  It 
is  also  certain  that  disinfection  of  excreta  is  practiced  to  such 
a  slight  extent  as  to  accomplish  very  little.  The  fact  that 
for  years  the  city  has  had  no  outbreak  of  disease,  and  no 
excess  due  to  the  water,  as  is  shown  by  the  typhoid  death 
rate  which  for  several  years  has  varied  from  seven  to  twenty- 
six  per  one  hundred  thousand,  indicates  that  the  typhoid 
bacilli,  which  are  being  continually  deposited  on  the  water- 
shed, fail  to  multiply.  Exactly  similar  conditions  prevail  on 
the  watersheds  of  Pawtucket,  Newport,  Woonsocket,  Hart- 
ford and  New  Haven,  only  to  mention  those  cities  in  my 
neighborhood  with  which  I  am  personally  familiar.  And  the 
general  testimony  of  all  epidemiologists  is  that  municipal 
water  supplies  are  never  continuously  infected  unless  com- 
paratively fresh  excreta  from  typhoid-infected  persons  pass 
directly  and  continuously  into  them.  Nevertheless  it  is  cer- 
tain that  typhoid  bacilli  must  be  continually  discharged  onto 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      15 

the  soil,  and  we  are  justified  in  considering  the  freedom  from 
infection  of  the  surface  waters  coming  from  such  areas  a 
strong  evidence  that  the  growth  of  the  typhoid  bacillus  out- 
side the  body  does  not  commonly  occur,  and  is  a  negligible 
factor  in  the  causation  of  the  disease. 

Cholera.  —  Early  investigators,  as  Nicati  and  Rietsch, 
working  with  sterilized  soil  and  water,  found  that  cholera 
spirilla  would  live  outside  the  body  sometimes  as  long  as  2 
months.  But  all  the  more  recent  workers  agree  that  under 
natural  conditions,  in  unsterihzed  materials,  the  life  of  the 
organism  is  quite  short.  Loesner^  recovered  the  germs  from 
dead  bodies,  which  had  been  artificially  injected,  as  late  as 
the  twenty-eighth  day.  Houston'  says  that  they  usually  die 
off  in  the  surface  layers  of  the  soil  in  12  days,  though  they 
may  be  kept  alive  longer  if  the  soil  is  watered  with  liquid 
manure.  Though  Heiser^  states  that  the  spirillum  was  found 
in  the  quiet  water  in  the  bends  of  the  Passig  river,  no  evi- 
dence was  presented  to  show  that  it  grew  there.  Gotschlich^ 
states  that  the  spirillum  is  rarely  found  in  feces  for  more  than 
three  days,  and  quotes  Abel  and  Draer,  Claussen  and  Dun- 
bar, and  refers  to  Koch,  as  stating  that  it  dies  in  dirty  canal 
water  in  24  to  30  hours.  In  unsterihzed  milk  it  may  live 
from  1  to  2  days,  but  dies  as  soon  as  the  milk  becomes  sour. 
All  these  agree  that  there  is  not  the  slightest  evidence  that 
the  cholera  spirillum  can  increase  in  numbers  outside  of  the. 
body.  On  the  other  hand,  Emmerich  and  Gemiind'  claim 
that  it  does  increase  in  numbers  in  the  soil,  and  may  be  found 
for  two  and  one-half  months.    Paladino-Blandini"  also  states 

»  Loesner,  Arb.  a.  d.  k.  Gsndhtsamte.  Berl.,  1896,  XII,  448. 
»  Houston,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1898-9,  XXVIII, 
413. 

»  Heiser,  Philippine  J.  Sci.  (Med.),  1908,  III,  92. 

*  Kolle  u.  Wa.ssermann,  Handhueh  [etc.],  Jena,  1904,  IV,  108. 

'  Emmcrifh  and  CJcmiind,  Miinrhcn  mod.  Wclinsohr.,  1004,  LI,  1089, 
1157. 

•  Centralbl.  f.  Haktcriol.  [etc.],  I,  .\bt.  Kef.,  Jena,  1905,  XXXVI,  53. 


16  THE  SOURCES  AND  MODES  OF  INFECTION 

that  it  may  grow  in  polluted  soil.  Koch^  says  that  it  grows 
only  in  the  human  body. 

Cholera  and  Soil.  —  There  is  certainly  a  great  deal  of  clin- 
ical evidence  that  it  does  not  increase  in  the  soil,  but  on  the 
contrary  speedily  dies  out.  The  epidemic  of  cholera  in 
Europe  in  1885  was  very  widespread  in  Italy  and  Spain. 
How  extensively  it  prevailed  and  what  a  great  number  of 
towns  and  villages  were  infected  are  well  shown  in  the  excel- 
lent report  prepared  by  Shakespeare.'  Nevertheless  by  the 
succeeding  year  it  had  entirely  disappeared  from  Spain,  and 
largely  from  Italy.  Turkey  had  a  similar  experience.^  We 
know  that  with  the  sanitary  conditions  prevailing  in  those 
countries  at  that  time  the  soil  must  have  been  infected  with 
cholera  in  countless  places.  But  cholera  rarely  recurred,  and 
when  it  did,  it  was  in  large  cities,  where,  the  most  probable 
explanation  is,  it  was  maintained  during  the  interval  by  mild 
unrecognized  cases  or  latent  infections.  The  extensive  epi- 
demic in  the  United  States  in  1873  was  not  followed  by  a 
recurrence  in  the  succeeding  year.  Not  only  is  epidemiologi- 
cal evidence  strongly  against  the  saprophytic  existence  of 
cholera  in  temperate  climates,  but  it  is  equally  so  for  tropical 
regions.  The  great  outbreak  in  the  Philippine  Islands  in 
1902-3  attacked  hundreds  of  villages,  and  soil  infection  was 
universal,  yet  the  disease  speedilydiedoutall  over  the  islands.* 
In  1905  there  was  a  similar  experience. 

In  the  Philippine  Islands  during  the  latter  outbreak 
it  was  believed  that  the  cooked  food  offered  for  sale  in  the 
streets  was  a  frequent  vehicle  of  cholera  germs,  and  a  num- 
ber of  samples,  particularly  of  boiled  rice,  were  found  to  con- 
tain the  spirilla.^     The  rice  was  probably  contaminated  by  the 

*  Koch,  Die  Bekampfung  des  Typhus,  Berhn,  1903,  14. 

'  Shakespeare,  Rep.  on  Cholera  in  Europe  and  India,  U.  S.  Gov. 
Print.  Off.,  Wash.,  1890. 

»  Clemow,  Tr.  Epidemiol.  Soc,  Lond.,  1904,  n.  s.,  XXIII,  223. 

*  Woodruff,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  1160. 
'  Maus,  Med.  News,  N.  Y.,  1902,  LXXXI,  318. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      17 

hands  of  sellers  or  purchasers.    Whether  the  spirilla  increased 
in  numbers  is  not  known. 

Mediterranean  Fever.  —  Mediterranean  or  Malta  fever 
has  long  been  recognized  as  endemic  at  various  points  on  the 
shores  of  the  Mediterranean,  particularly  on  the  island  of 
Malta.  It  shows  all  the  characters  of  "  endemic  "  disease, 
being  confined  to  certain  areas  and  exhibiting  little  tendency 
to  pass  to  other  parts  of  the  world,  or  to  extend  by  contagion. 
The  micrococcus,  M.  melitensis,  which  is  its  cause,  was  dis- 
covered by  Bruce  in  1887  and  has  been  very  carefully  studied 
by  an  English  commission  acting  under  the  supervision  of 
the  Roj^al  Society.  This  commission,  as  have  independent 
observers,  has  given  much  study  to  the  vitality  of  the  spe- 
cific organism  of  the  disease  outside  of  the  body.  The  evi- 
dence seems  to  be  that  it  tends,  like  other  disease  germs,  to 
perish  when  removed  from  the  body  and  deprived  of  nourish- 
ment and  moisture  and  exposed  to  light  and  heat,  but  it  may 
retain  its  vitality  for  weeks  and  even  months  under  certain 
conditions,  behaving  in  this  respect  much  like  the  typhoid 
bacillus.^  No  direct  experiments  seem  to  have  been  made  to 
determine  whether  it  ever  maintains  a  saprophytic  existence 
in  the  soil,  but  its  habits  of  life  are  such  that  it  is  a  fair  in- 
ference that  it  can  rarely  do  so,  and  that  such  saprophytic 
growth,  if  it  ever  takes  place,  is  of  no  greater  practical  impor- 
tance than  is  the  saprophytic  growth  of  typhoid  germs.  The 
micrococcus  was  carefully  sought  for  in  water  and  in  dust, 
but  was  never  found."  The  disease  is  referred  to  in  this  con- 
nection because,  on  account  of  its  localization  and  slight 
apparent  contagiousness,  it  was  believed  by  many  medical 
men,  as  well  as  the  laity,  to  spring  from  the  soil.  Yet  the 
work  of  the  English  investigators  has  conclusively  shown 
that  the  chief  source  of  the  disease  is  the  herds  of  infected 
goats.  It  is  by  the  infected  milk  of  these  that  the  disease 
is  transmitted  to  human  beings.     It  is  barely  possible  that 

'  Report  of  Commission  of  Royal  Society,  1901,  Pts.  I  and  II. 
»  Bruce,  Nature,  Lond.,  1908,  LXXVIII,  40. 


18  THE  SOURCES  AND  MODES  OF  INFECTION 

the  fever  may  be  spread  to  some  extent  by  contact  with 
infected  urine  either  of  goats  or  of  men,  just  as  typhoid 
fever  frequently  extends  by  contact  infection,  but  the  fact 
that  thousands  of  infected  men  have  been  invahded  home 
to  England  without  any  extension  of  the  disease  in  that 
country  would  indicate  that  such  occurrence  is  extremely 
rare. 

Bubonic  Plague.  —  The  germ  of  buljonic  plague  is  not  so 
resistant  as  is  that  of  typhoid  fever,  nor  yet  is  it  of  such  feeble 
vitality  as  that  of  cholera.  It  is  rather  susceptible  to  disin- 
fectants, to  high  temperature  and  to  drying,  but  in  a  moist 
condition,  particularly  at  low  or  moderate  temperatures,  may 
remain  alive  for  some  months.^  The  endemicity  of  the  dis- 
ease in  many  localities  has  led  some  to  assume  that  it  devel- 
ops in  the  soil,  but  the  most  careful  students  see  no  necessity 
for  assuming  soil  infection  to  account  for  its  diffusion,  and 
there  is  ample  positive  evidence  that  plague  is  derived  from 
other  sources.  Yet,  in  view  of  the  fact  that  soil  infection 
has  been  so  much  discussed,  it  is  rather  remarkable  that  so 
few  actual  experiments  have  been  made  to  test  the  theory. 
Perhaps  it  is  because  such  experiments  are  difficult  and 
those  who  are  most  competent  to  make  them  have  thought 
their  time  better  occupied  with  work  giving  better  promise 
of  positive  results.  Elliot "  found  that  soil  naturally  infected 
would  cause  the  disease  in  rats  after  an  interval  of  a  month, 
and  Watkins-Pitchford  ^  in  some  careful  experiments  found 
that  inoculated  soil  retained  its  virulence  for  four  weeks,  but 
not  for  five  weeks.  The  soil  was  not  sterilized.  Gladin^ 
found  the  bacillus  alive  in  unsterile  moist  earth  after  2 

*  Rosenau,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab. 
Bull.  No.  4,  1901.     See  also  Simpson,  A  Treatise  on  Plague. 

'  Elliot,  Lancet,  Londr,  1905,  I,  1562. 

3  Watkins-Pitchford,  Rep.  Gov.  Bacteriologist,  Pietermaritzburg, 
1903  [Report  on  Plague,  31]. 

*  Gladin,  Centralbl.  f.  Bakteriol.  [etc.],  I,  Abt.  Orig.,  Jena,  1898, 
XXIV,  588. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      19 

months,  and  Rosenau  ^  kept  it  alive  a  long  time  in  cool  moist 
garden  earth,  and  the  Indian  Plague  Commission,  1901,  did 
the  same  in  moist  sterile  cow  dung.  Other  experiments  by 
Mackie  and  Winter  in  Bombay,  cited  in  the  Journal  of  Hy- 
giene,^ were  with  grossly  infected  cow  dung  from  the  floor  of  a 
native  house.  No  pest  bacilli  were  recovered  by  culture  on 
inoculation  after  96  hours.  Further  careful  experiments  have 
been  made  by  the  Indian  Commission  of  1905.  Their  con- 
clusions are  as  follows: 

"Floors  of  cow  dung  grossly  contaminated  with  the  bacillus 
of  plague  remain  infective  for  48  hours ;  floors  of  a  sort  of  na- 
tive cement  for  24  hours,  the  infectivity  being  tested  in  each 
case  by  inoculation.  The  floors  were  infective  to  animals 
allowed  to  run  on  them  for  only  half  the  above  time." 

Thus  there  appears  to  be  no  bacteriological  evidence  that 
the  bacillus  of  plague  grows  outside  of  the  bodies  of  living 
animals,  and  a  great  deal  of  evidence  that  when  separated 
from  the  body  it  tends  to  die  off  more  or  less  rapidly  and  fre- 
cjuently  very  rapidly.  The  Indian  Plague  Commission  con- 
siders that  reports  of  soil  infections  are  unworthy  of  credence 
unless  continuous  and  careful  observations  on  the  presence 
of  rats  and  fleas  have  been  made. 

Dysentery  Bacillus.  —  One  form  of  dysentery  is  caused  by 
a  bacillus  belonging  to  the  colon  group,  and  it  has  a  number 
of  sub-varieties.  It  is  not  quite  so  resistant  as  the  typhoid 
bacillus,  but  it  has  been  known  to  survive  all  winter  in  damp 
carth.'^  It  is  said  that  in  Japan  local  outbreaks  often  persist 
longer  than  do  outbreaks  of  cholera,  perhaps  due  to  the  higher 
resistance  of  the  germ.*    The  bacilli  appear  to  be  easily  de- 

^  Rosenau,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 
No.  4,  1901,  9. 

'  J.  Hyg.,  Cambridge,  1906,  VI,  511. 

'  Schmidt,  Centralbl.  f.  Bakteriol.  [etc.],  I,  Abt.  Orig.,  Jena,  1902, 
XXXI,  522. 

*  Eldridge,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Pub.  Health 
Rep.,  1901,  1. 


20  THE  SOURCES  AND  MODES  OF  INFECTION 

stroyed  by  other  bacteria,  for  they  can  rarely  be  found  in  feces 
after  two  days.^ 

Dysentery  Ameba.  —  Another  form  of  dysentery  occur- 
ring chiefly  in  the  tropics  is  caused,  not  by  a  bacterium,  but 
by  an  ameba,  which  is  one  of  the  lower  forms  of  animal,  not 
vegetable  life.  The  researches  of  Musgrave  and  Clegg  ^  show 
that  there  are  many  forms  of  amebse,  probably  distinct 
species,  and  that  they  grow  in  the  soil  and  on  various  kinds 
of  vegetables.  They  can  be  grown  on  culture  media  at  room 
temperature  and  produce  the  disease  in  monkeys  and  men. 
They  may  become  encysted  and  then  are  quite  resistant 
to  drying.  The  question  of  the  identity  of  the  saprophytic 
and  pathogenic  amebse,  which  is  maintained  by  the  writers 
just  named,  is  still  suhjudice.  and  will  be  again  referred  to  in 
Chapter  II. 

Bacteria  of  Suppuration. — The  formation  of  pus  in  wounds, 
abscesses,  or  elsewhere,  is  practically  always  the  result  of 
infection  by  bacteria.  Very  many  varieties  of  bacteria  may 
occasionally  cause  suppuration,  but  a  few  species  such  as 
the  Micrococcus  aureus,  M.  albus  and  M.  citreus,  and  Strep- 
tococcus pyogenes,  are  by  far  the  most  common  cause  of  this 
process.  I  have  never  had  occasion  to  pay  much  attention 
to  the  habitat  of  these  bacteria,  but  according  to  Gotschhch  ^ 
they  are  constantly  found  growing  in  the  skin  and  on  the 
mucous  surfaces.  References  are  of  course  given  in  his  article 
to  numerous  original  investigations,  but  among  more  recent 
observations  may  be  mentioned  those  of  Ruediger,^  Gordon  ^ 
and  Hess."    These  bacteria  are  also  found  in  the  tonsils  and 

1  Kruse,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  370,  386. 
'  Musgrave  and  Clegg,  Bull.  No.  18,  Bu.  Gov.  Lab.  P.  I. 

*  Gotschlich,  Kolle  and  Wassermann,  Handbuch  [etc.],  Jena, 
1902,  I,  147. 

*  Ruediger,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVII,  1172. 

'  Gordon,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1904-5,  XXXIV, 
387. 

«  Hess,  Centralbl.  f.  Bakteriol  [etc.],  I,  Abt.  Orig.,  Jena,  1907, 
XLIV,  1. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      21 

lymph  glands,  apparently  remaining  latent  for  long  periods 
of  time,  i.e.,  not  causing  suppuration.  Bacteria  such  as  the 
above,  which  are  the  constant  parasites,  or  perhaps  rather 
commensals  of  man,  are  naturally  to  be  looked  for  in  the 
vicinity  of  man  and  on  the  surfaces  of  the  body,  on  clothing, 
utensils,  furniture;  and  the  dust  and  dirt  of  all  places  fre- 
quented by  human  beings  are  found  to  contain  more  or  less  of 
them.  They  may  also  be  found  in  polluted  waters.  But 
whether  under  natural  conditions  they  are  commonly  able 
to  maintain  a  saprophytic  existence  is  another  matter.  Judg- 
ing from  what  I  have  read  in  the  text-books  I  should  suppose 
that  the  pus  organisms  are  not  so  limited  as  to  the  conditions 
of  their  growth  as  are  most  disease-producing  bacteria.  They 
are  not  so  dependent  on  a  high  and  even  temperature  or  on 
the  composition  of  the  medium  on  which  they  grow.  I  should 
suppose  that  they  would  be  more  likely  to  maintain  a  sap- 
,  rophytic  existence  than  most  other  pathogenic  organisms,  yet 
I  do  not  know  that  such  existence  for  them  has  ever  been 
demonstrated.  In  fact  Gotschlich^  says  that  they  are  not 
saprophytes.  Bacillus  pyocyaneus  has,  however,  been  found, 
by  Gorham,  growing  in  a  heap  of  moist  rags  at  a  paper  mill. 
Diphtheria. —  Diphtheria  was  not  so  very  long  ago  believed 
to  be  a  "  filth  disease,"  that  is,  its  germs  were  supposed  to 
have  a  habitat  outside  of  the  body  in  various  forms  of  "  dirt." 
This  theory  was  common  during  my  medical-school  daj's,  and 
when  I  began  health-department  work  in  1884,  I  tried  to  fit 
the  facts  as  I  saw  them  to  this  theory.  But  they  did  not 
fit,  and  the  impression  continued  to  grow  that  diphtheria 
was  a  purely  contagious  disease.  The  life  habits  of  the  diph- 
theria bacillus  indicate  that  while  it  is  more  resistant  than 
some  other  disease-producing  organisms  next  to  be  men- 
tioned, and  somewhat  easier  to  cultivate,  it  is  very  unlikely 
that  it  is  able  to  propagate  itself  outside  of  the  body,  except 
at  times  in  milk.     Houston,"  while  he  does  not  consider  his 

^  Gotechlich,  Kolle  and  Wassermann,  Handbuch  [etc.],  Jena,  IV,  173. 
«  Houston,  Loc.  Gov.  Bd.  Rep.  of  Med.  Off.,  1898-9,  XXVIII,  413. 


22  THE  SOURCES  AND  MODES  OF  INFECTION  ' 

experiments  conclusive,  believes  that  the  bacillus  of  diph- 
theria dies  off  very  quickly  in  unsterilized  soils  of  various 
kinds.  Graham-Smith^  cites  a  number  of  writers  concerning 
the  vitality  of  the  organism  in  water  and  milk.  According 
to  Seller  and  Stoutz,  it  multiplies  in  sterilized  water  for  a 
while,  but  Montefusco  and  D'Espine  and  Marignac  found 
no  evidence  of  multiplication  even  in  distilled  water,  and  in 
polluted  water  it  dies  in  6  days.  Schottelius  reported,  con- 
trary to  general  experience,  that  the  bacillus  multiplies  more 
rapidly  in  raw  than  in  sterile  milk,  while  Montefusco  found 
no  multiplication  in  raw  milk  after  3  days,  and  Rubinstein 
found  that  the  bacilli  died  in  24  hours.  Eyre  showed  that 
in  milk  drawn  in  as  sterile  a  condition  as  possible  the  diph- 
theria like  the  typhoid  bacillus  undergoes  rapid  multiplica- 
tion. Kersten,^  on  the  other  hand,  reports  that  diphtheria 
bacilli  will  persist  in  raw  milk  for  72  days,  and  though 
they  undergo  no  increase  at  first,  do  so  later.  Montefusco 
found  that  they  died  in  fresh  bread  in  24  hours.  Except  in 
fairly  fresh  milk  at  room  temperature,  it  is  unlikely  that  the 
bacilli  of  diphtheria  multiply  outside  of  the  body. 

Other  Diseases.  —  Tuberculosis,  pneumonia,  influenza, 
cerebro-spinal  meningitis,  gonorrhea  and  syphilis  are  caused 
by  organisms  which  are  difficult  to  cultivate,  and  I  think  all 
bacteriologists  agree  that  it  is  futile  to  seek  for  their  habitat 
outside  of  the  bodies  of  men  or  other  animals.  As  for  the 
protozoan  diseases,  such  as  malaria  and  sleeping  sickness, 
such  a  habitat  is  still  more  improbable.  It  is  only  recently, 
and  after  laborious  experiment,  that  any  of  this  class  of 
organisms  have  been  cultivated  in  the  laboratory.  That  they 
grow  outside  of  the  body  under  ordinary  conditions  is  in  the 
highest  degree  improbable.  There  is  one  protozoan,  however, 
the  dysentery  ameba,  which,  if  recent  observations  are  cor- 
rect, does  live  outside  of  the  body.    But  this  organism  belongs 

^  Nuttall  and  Graham-Smith,  The  Bacteriology  of  Diphtheria,  Cam- 
bridge, 1898,  171. 

^  Kersten,  Arb.  a.  d.  k.  Gsndhtsamte.,  Berl.,  1909,  XXX,  341. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      23 

to  an  entirely  different  class  from  the  blood  parasites,  and 
while  the  facts  so  far  known  render  it  not  improbable  that 
the  amcba  does  grow  outside  of  the  bod}^,  the  facts  in  regard 
to  blood  parasites  are  against  any  such  hypothesis. 

Summary  of  Laboratory  Evidence.  —  It  appears,  then,  that 
so  far  as  experimental  evidence  is  concerned  there  is  no  war- 
rant for  assuming  a  source  for  the  common  infectious  diseases 
outside  of  animal  bodies.  It  is  only  with  extreme  difficulty 
that  a  few  of  the  blood  parasites  belonging  to  the  protozoa 
can  be  cultivated,  and  the  cultivation  of  many  bacterial 
forms  is  strictly  limited,  so  that  it  is  hardly  possible  to  ima- 
gine their  maintaining  a  saprophytic  existence.  It  is  true 
that  the  bacteria  of  typhoid  fever  and  perhaps  cholera,  dysen- 
tery, and  diphtheria  may  be  conceived  of  as  growing  outside 
of  the  body  under  natural  conditions,  but  such  growth,  if  it 
ever  occurs,  must  be  rare. 

Lack  of  Epidemiological  Evidence.  —  Nevertheless  during 
the  larger  part  of  the  nineteenth  century  it  was  common  to 
seek  such  an  outside  source  for  most  of  the  infectious  diseases. 
The  filth  theory  of  disease,  the  vogue  of  which  was  largely 
due  to  Chadwick,  Murchison  and  Pettenkoffer,  assumed  that 
the  specific  poison  of  many  of  our  common  infectious  diseases, 
and  particularly  of  typhoid  fever  and  cholera,  developed  in 
a  contaminated  soil,  or  in  other  forms  of  filth.  There  was  at 
that  time  no  knowledge  of  the  micro-organisms  which  cause 
disease,  and  the  theories  of  the  origin  of  disease,  so  far  as 
they  had  any  basis  at  all,  depended  on  clinical  or  epidemio- 
logical evidence.  There  was,  it  is  true,  some  epidemiological 
evidence  for  l)elieving  that  typhoid  fever  and  cholera  could 
develop  in  filth,  for  both  of  these  are  excrement-borne  dis- 
eases, and  it  was  difficult  to  decide  without  any  knowledge 
of  the  bacteria  which  cause  them  whether  they  developed 
in  filth  or  were  merely  transmitted  in  filth.  But  as  regards 
ty[)ims  fever,  smallpox,  scarlet  fever,  measles,  diphtheria 
and  similar  diseases,  there  is  really  no  epidemiological  evi- 
dence to  suggest  that  they  develop  outside  of  the  body.    If 


24  THE  SOURCES  AND  MODES  OF  INFECTION 

a  disease  does  have  its  source  in  the  outer  world,  we  should 
expect  to  find  it  locaHzed,  attached  to  a  definite  locality, 
endemic,  as  it  was  formerly  called.  The  somewhat  well-de- 
fined infected  area  we  should  expect  to  maintain  its  infection 
for  some  time,  and  we  should  expect  persons  coming  into  the 
area  to  become  infected.  But  if  we  watch  the  outbreaks, 
especially  the  smaller  outbreaks,  of  such  diseases  as  measles, 
smallpox,  scarlet  fever,  diphtheria,  etc.,  which  occur  in  dif- 
ferent sections  of  cities,  or  in  villages,  we  find  nothing  to 
indicate  place  infection.  A  "  pin  map  "  of  these  diseases  in 
a  city  shows  first  one  or  two  pins,  indicating  infected  houses, 
then  more  appearing  day  by  day  in  the  surrounding  section, 
until  there  are  ten  or  twenty  or  a  hundred  cases  within 
the  radius  of  a  block  or  a  few  blocks  or  half  a  mile.  The 
scattered  groups  of  houses  are  of  a  somewhat  circular  form, 
a  little  denser  nearer  the  center.  The  outbreak  lasts  a  few 
weeks,  or  two  or  three  months,  and  then  disappears,  only  to 
reappear  in  another  part  of  the  city.  In  village  outbreaks 
contagion  is  usually  more  clearly  traced.  The  importation 
of  the  disease  and  the  sequence  of  the  earlier  cases  are  often 
made  out.  The  outbreak  lasts  only  for  a  moderate  time,  and 
then  the  disease  disappears,  usually  not  to  return  for  a  con- 
siderable time,  often  for  years.  There  is  nothing  to  indicate 
soil  infection.  If  these  diseases  really  come  from  privy 
vaults,  sink  drains  and  garbage  heaps,  we  should  expect  a 
very  different  distribution  in  the  house  from  what  is  actually 
found.  The  ground  floor  is  not  oftener  infected  than  the 
upper  floor,  nor  (for  some  might  say  that  rising  currents  carry 
disease  germs  to  the  top  of  the  house)  the  upper  than  the 
lower.  But  what  is  most  important,  when  one  family  in  a 
house  is  attacked  with  such  a  disease  as  diphtheria,  we  should 
expect  the  other  families  to  be  usually  attacked  also,  if  the 
disease  is  a  disease  of  locality.  But  in  Providence  statis- 
tics for  the  last  twenty  years  show  that  in  scarlet  fever  and 
diphtheria  in  only  about  seven  per  cent  of  the  houses  does 
the  disease  extend  from  one  family  to  another.    In  most  of 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      25 

these  cases  of  extension,  direct  contact  between  members  of 
the  families  is  shown  to  have  taken  place. 

In  such  important  diseases  as  smallpox,  measles  and  scarlet 
fever,  the  germs  of  which  have  not  been  isolated,  as  well  as 
in  typhus  fever,  diphtheria  and  whooping  cough,  epidemio- 
logical evidence  of  an  extra-corporal  origin  is  entirely  lack- 
ing. Epidemiological  and  laboratory  evidence  are  against 
the  growth  of  disease  germs  outside  of  the  body  under 
ordinary  circumstances.  The  notion  still  common,  even 
among  physicians  and  health  officers,  that  these  infectious 
diseases  are  filth  diseases,  as  that  term  is  ordinarily  under- 
stood, is  absolutely  without  foundation. 

Typhoid  Fever  and  Cholera.  —  Typhoid  fever  and  cholera 
not  infrequently  appear  in  small  contact  outbreaks  very 
similar  to  those  of  scarlet  fever  and  diphtheria,  but  being 
excrement-borne,  contact  infection  is  not  so  common  as  in 
the  latter,  while  infection  by  water  and  food  is  more  common. 
Some  outbreaks  of  tj^phoid  fever  may  undoubtedly  be  inter- 
preted as  due  to  soil  infection,  but  they  can  also  be  explained 
otherwise,  and  the  bacteriological  evidence  is  so  strongly 
against  the  soil  hypothesis  that  we  are  not  justified  at 
present  in  assuming  it.  There  is  no  evidence  that  cholera 
finds  a  habitat  in  the  soil  of  temperate  climates,  and  the 
most  careful  observers  in  the  tropics  are,  I  think,  agreed 
that  it  is  not  different  there.  The  same  is  true  of  bubonic 
plague. 

Yellow  Fever  and  Malaria.  —  There  is  a  class  of  diseases 
for  which  there  seemed,  at  one  time,  to  be  very  strong  evi- 
dence that  the  cause  which  produced  them  had  its  origin  out- 
side of  the  body.  I  refer  to  yellow  fever,  malaria,  sleeping 
sickness  and  the  blood-parasite  diseases  of  cattle.  Malaria 
is  one  of  the  best  defined,  oldest,  and  best  understood  of 
diseases.  I  suspect  that  for  twenty-five  hundred  years  what 
has  been  known  of  malaria  has  decidedly  colored  prevailing 
views  as  to  the  nature  and  source  of  many  other  infectious 
diseases.    Malaria  is  a  typical  endemic  disease.    Its  localiza- 


26  THE  SOURCES  AND   MODES  OF  INFECTION 

tion  can  scarcely  be  better  illustrated  than  in  my  own  neigh- 
borhood. During  the  latter  half  of  the  nineteenth  century 
the  southern  part  of  New  England  suffered  from  extensive 
outbreaks  of  malarial  disease.  The  whole  country  was  by  no 
means  affected,  but  well-defined  limited  areas  of  infection  were 
to  be  noted  all  over  the  region,  and  in  different  portions  of 
some  of  the  cities.  Infection  in  many  of  these  persisted  from 
year  to  year.  People  moving  into  them  became  sick,  and 
malaria  was  escaped  by  moving  away.  Most  of  these  areas 
were  in  close  proximity  to  swampy  land  and  marshes,  others 
were  some  little  distance  removed,  but  usually  in  the  direc- 
tion of  the  prevailing  winds.  Thus  there  was  presented  a 
perfect  picture  of  place  infection.  We  were  justified,  in  the 
then  existing  state  of  knowledge,  in  assuming  that  the  mala- 
rial poison  developed  in  the  wet  and  marshy  places  which 
were  closely  connected  with  these  infected  spots.  We  now 
know  that  this  assumption  was  incorrect,  though  it  was  very 
near  the  truth,  and  that  the  germs  of  malaria  do  not 
develop  in  the  marshes,  but  that  the  mosquitoes  which 
carry  the  germs  from  one  person  to  another  do  breed 
there.  As  far  as  sanitation  was  concerned  the  error  was 
not  serious.  The  new  facts  have  simply  enabled  us  to 
work  more  economically,  by  determining  accurately  just 
what  wet  places  are  dangerous.  But  the  apparent  certainty 
that  the  malarial  virus  developed  outside  of  the  body  had 
enormous  influence  in  encouraging  the  belief  that  other 
disease  poisons  also  had  an  extraneous  origin.  The  history 
of  yellow  fever  is  somewhat  similar  to  that  of  malaria.  It  is 
eminent4y  a  place  disease.  So  are  sleeping  sickness  and  Texas 
cattle  fever  and  a  number  of  other  diseases.  All  of  this  group 
we  now  know  are  transmitted  by  insects,  and  it  is  the  insects 
which  have  an  extraneous  existence  and  not  the  parasite  of 
the  disease.  The  mico-organisms  which  cause  these  diseases 
do  not  grow  outside  of  the  bodies  of  human  beings  or  other 
animals  which  serve  as  hosts,  or  of  the  insects  which  serve  as 
carriers. 


LIFE  OF  DISEASE  GERMS  OUTSIDE  OF  THE  BODY      27 

Review  of  Evidence.  —  In  reviewing  this  subject  we  are 
forced  to  the  conclusion  that  while  it  is  possible  that  the 
anthrax  and  tetanus  bacilli  and  the  pus-forming  bacteria 
may  develop  in  the  soil,  there  is  no  evidence  that  they  com- 
monly do  so.  It  is  also  possible  that  the  typhoid  bacilli,  and 
to  a  still  less  extent  the  bacteria  of  cholera,  dysentery  and 
plague,  maintain  a  limited  saprophytic  existence,  but  this  is 
probably  very  unusual.  There  is  ample  epidemiological  evi- 
dence that  in  temperate  climates  such  a  source  for  these 
diseases  must  be  an  almost  infinitesimal  factor  in  their 
development.  Probably  the  diphtheria  bacillus  never  has  a 
saprophytic  growth  of  any  significance,  unless  possibly  very 
rarely  in  milk.  As  for  tuberculosis,  pneumonia,  influenza, 
cerebro-spinal  meningitis,  scarlet  fever,  typhus  fever,  small- 
pox, whooping  cough,  gonorrhea  and  syphilis,  malaria,  yellow 
fever  and  sleeping  sickness,  there  is  not  the  slightest  reason 
for  supposing  that  they  ever  develop  outside  of  the  bodies  of 
animals.  * 

Changes  in  Present  Theories  and  Practice.  —  If  these  facts 
are  correct — and  I  can  scarcely  believe  that  any  will  seriously 
contend  that  we  have  any  evidence  that  an  appreciable 
amount  of  our  common  infectious  diseases  arises  in  the  exter- 
nal world — prevailing  notions  as  to  the  sanitary  functions  of 
the  state  should  be  decidedly  modified.  The  laity  and  the  lay 
press  still  believe  that  most  of  the  infectious  diseases  have 
their  origin  outside  of  the  body,  in  filth,  or  if  admitting  con- 
tagion, attach  equal  importance  to  external  sources  of  infec- 
tion. And  even  very  many  health  officials  and  some  teachers 
and  writers  on  sanitation  hold  the  same  view.  Municipal 
sanitation  and  municipal  cleansing  are  still  synonymous 
terms  to  many  health  officers.  It  is  true  enough  that  two  or 
three  diseases,  as  typhoid  fever  and  cholera,  the  germs  of 
which  are  found  in  human  excrement,  have  markedly  dimin- 
ished as  a  result  of  improved  methods  of  excrement  disposal, 
or  because  of  the  introduction  of  water  sujiplies  uncontami- 
nated  with  human  excrement.    It  is  also  doubtless  true  that 


28  THE  SOURCES  AND  MODES  OF  INFECTION 

whatever  promotes  municipal  cleanliness  tends  to  promote 
personal  cleanliness,  and  real  personal  cleanliness,  as  we 
shall  see,  is  doubtless  an  important  factor  in  the  preven- 
tion of  contagion.  But  except  for  one  or  two  diseases, 
and  except  for  very  indirect  effects,  the  cleansing  of  streets, 
alleys,  and  back  yards,  of  dwellings  and  stables,  the  regula- 
tion of  offensive  trades,  and  the  prevention  of  nuisances 
generally,  have,  so  far  as  we  can  see,  no  relation  to  the  general 
health,  nor  any  value  in  the  prevention  of  specific  diseases. 
While  municipal  improvements  such  as  the  above  are  desir- 
able, there  is  little  more  real  reason  why  health  officials 
should  work  for  them,  than  there  is  that  they  should  work 
for  free  transfers,  cheaper  commutation  tickets,  lower  prices 
for  coal,  less  shoddy  in  clothing  or  more  rubber  in  rubbers,  — 
all  good  things  in  their  way  and  tending  towards  comfort  and 
health. 


CHAPTER  II. 

CARRIERS    AND    MISSED    CASES. 

A  Recent  Discovery.  —  That  there  are  occasionally  seen 
mild  cases  of  the  infectious  diseases  diflBcult  or  impossible  to 
recognize,  has  long  been  known.  That  such  cases  are  rare 
has  always  been  generally  believed.  That  the  germs  of  dis- 
ease can  maintain  themselves  and  increase  in  number  in  a 
person  without  causing  any  symptoms  at  all,  was  until 
recently  scarcely  thought  possible,  and  the  idea  that  such 
latent  infections  are  extremely  common  would  have  been 
scouted  as  preposterous.  Even  to-day  the  facts  are  denied 
by  many  sanitary  officials,  and  there  are  comparatively  few 
who  recognize  the  frequency  with  which  mild  atypical  forms 
of  disease  and  healthy  "  carriers  "  of  germs  are  found,  or 
realize  the  tremendous  importance  which  such  cases  have  in 
the  spread  of  the  contagious  diseases.  Undoubtedly  the  most 
fruitful  medical  discovery  of  the  last  century,  and  perhaps  of 
all  time,  was  the  discovery  of  the  parasitic  nature  of  the 
infectious  diseases.  Probably  the  most  important  discovery 
bearing  on  preventive  medicine  since  the  demonstration  of  the 
bacterial  origin  of  disease,  is  that  disease  germs  frequently 
invade  the  body  without  causing  disease.  The  succeeding 
pages  will  be  devoted  to  a  consideration  of  some  of  the  data 
available  concerning  the  existence  of  mild  cases  and  carriers. 
The  term  "  carrier"  is  applied  to  those  persons  in  whom  patho- 
genic micro-organisms  exist,  but  who,  nevertheless,  show  no 
symptoms.  vSuch  carriers  are  rarely  found  by  the  health  offi- 
cer, and  the  very  mild  cases  also  naturally  escape  notice  and 
are  hence  called  by  the  English  "  missed  cases,"  i.e.,  casee 
which  fail  of  recognition. 

29 


30  THE  SOURCES  AND  MODES  OF  INFECTION 

Typhoid  Fever  not  an  Intestinal  Disease.  —  Bacteriolo- 
gists are  coming  to  look  upon  typhoid  fever  as  essentially  an 
infection  of  the  blood  rather  than  a  disease  of  the  intestines. 
Frequently  the  intestinal  lesions  are  slight,  and  often  the 
bacilli  are  few  in  number  in  the  feces,  and  sometimes  they 
cannot  be  found  at  all.  Semple  and  Greig  ^  report  a  case  of 
typhoid  fever  in  which  the  bacilli  were  found  in  the  blood 
from  July  20th  to  September  20th,  but  were  never  once  found 
in  the  feces  or  urine.'  So  far  as  we  know,  the  typhoid  bacil- 
lus may  enter  the  lymph  and  blood  from  any  portion  of  the 
alimentary  canal,  and  Semple  and  Greig,  Forster,  Kayser  and 
others  believe  that  it  frequently  enters  through  the  tonsils,  and 
Pratt,  Peabody  and  Long^  say  that  there  is  no  more  evidence 
of  entrance  through  the  intestines  than  through  the  tonsils. 
In  any  event  the  bacillus  is  soon  found  in  the  blood,  and  con- 
tinues in  this  fluid  through  the  acute  stages  of  the  disease. 
Typhoid  fever  is,  then,  as  was  first  pointed  out  by  Schott- 
mliller  in  1902,  essentially  a  bacteremia.  The  bacillus  may 
migrate  from  the  blood  to  any  organ.  As  has  been  shown  by 
Pratt,  Peabody  and  Long,  a  favorite  habitat  is  the  gall  blad- 
der. Pratt  found  it  in  the  gall  bladder  in  twenty-one  out  of 
thirty  cases.  It  may  also  infect  the  bones,^  kidneys,^  ovaries,^ 
urinary  bladder,  cerebro-spinal  fluid, ^  and  maybe  found  in  the 
bronchial  secretions  (Pratt,  Peabody  and  Long  cite  several 
authors  as  to  the  finding  of  the  bacillus  in  bronchial  mucus, 
and  state  that  Dieudonne  found  it  for  seven  weeks  after 
recovery).    Some  of  these  cases  give  no  evidence  of  intestinal 

1  Semple  and  Greig,  Scient.  Mem.,  Med.  and  Surg.  Dept.,  Gov.  of 
India,  1908,  XXXII,  9. 

2  See  also  Opie  and  Bassett,  cited  by  Pratt,  Peabody  and  Long. 

'  Pratt,  Peabody  and  Long,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX, 
846. 

*  Sultan,  Deutsche  med.  Wchnschr.,  1894,  XX,  675. 

^  Greaves,  Brit.  M.  J.,  Lond.,  1907,  II,  75. 

8  Lavenson,  Univ.  Penn.  Med.  Bull.,  1908-9,  XXI,  55;  Silber- 
berg,  Berl.  klin.  Wchnschr.,  1908,  XLV,  1354. 


CARRIERS  AND  MISSED  CASES  31 

infection.  Liidke^  experimenting  with  guinea  pigs  showed 
that  typhoid  bacilli  may  remain  latent  in  the  spleen  and  bone 
marrow  for  some  time.  Kelly  ^  says  that  tj'phoid  bacilli 
were  found  in  7  of  77  gall-bladder  operations,  and  he  states 
that  in  many  cases  there  is  no  evidence  of  intestinal 
infection.  Primary  cholecystitis  has  also  been  reported 
by  others. 

Typhoid  Bacilli  in  Urine.  —  That  typhoid  bacilli  may  per- 
sist in  the  body  without  causing  symptoms  has  been  known 
for  some  time,  but  the  importance  of  this  fact  has  been  recog- 
nized only  during  the  last  few  years.  When  the  gall  bladder 
or  the  urinary  tract  is  the  seat  of  the  persistent  infection, 
the  bacilli  may  be  discharged  in  the  feces  or  urine.  Richard- 
son^ has  shown  that  twenty-three  per  cent  of  all  typhoid  fever 
patients  after  recovery  have  typhoid  bacilli  in  their  urine, 
often  in  pure  culture  and  usually  in  large  numbers,  but  they 
generally  disappear  within  three  months.  Long-continued 
urinary  infection,  however,  does  sometimes  occur.  Thus 
Houston*  and  Cochrane ''  found  the  urine  infectious  for  three 
years. 

Typhoid  Bacilli  in  Feces.  —  Typhoid  bacilli  can  often  be 
recovered  from  the  feces  after  recovery,  as  well  as  from  the 
urine.  Graham,  Overlander  and  Dailey^  found  the  bacilli  in 
the  feces  of  11,  or  16.9  per  cent,  of  65  patients  10  dsLys  pre- 
vious to  their  discharge  from  the  hospital.  Semple  and  Greig 
found  that  11.6  per  cent  of  86  typhoid  convalescents  dis- 
charged bacilli  in  their  feces  for  over  6  weeks.  It  is  probable 
that  the  infection  generally  disappears  from  the  majority  of 
cases,  but  some  become  "chronic  carriers,"  and  the  bacilli 
may  often  be  found  in  enormous  numbers  in  the  feces  for 

»  Ludke,  Mimchen  med.  Wchnschr.,  1908,  LV,  1369. 

2  Kelly,  Am.  J.  M.  Sc.  Phila.,  1906,  n.  s.,  CXXXII,  447,  744. 

'  Richardson,  J.  Exper.  M.,  N.  Y.,  1898,  III,  349;  1809,  IV,  19. 

*  Houston,  Brit.  M.  J.,  Lond.,  1899,  I,  78. 

^  Cochrane,  J.  Roy.  Army  Med.  Corps,  Lond.,  1909,  XII,  155. 

"  Graham,  Overlander  and  Dailey,  Bost.  M.  &  S.  J.,  1909,  CLX,  38. 


32  THE  SOURCES  AND  MODES  OF  INFECTION 

years.  Four  and  one-half  years  is  the  longest  time  that 
typhoid  bacilli  have  been  shown  on  bacteriological  evidence 
to  have  persisted  in  the  feces.  There  is,  however,  epidemio- 
logical evidence  for  assuming  a  much  longer  continuance  of 
the  infection.  Dean  ^  reports  the  case  of  a  medical  man  who 
had  had  typhoid  fever  twenty-nine  years  before,  and  had 
since  then  frequent  attacks  of  biliary  colic.  Typhoid  bacilli 
were  recovered  from  his  feces.  It  was  believed  that  no  one 
had  contracted  the  disease  from  him,  but  he  had  always 
been  very  careful  in  his  personal  habits.  Huggenberg  ^ 
noted  thirteen  cases  in  a  household  extending  over  a 
period  of  thirty-two  years.  One  woman  who  had  the  disease 
in  1877  was  shown  to  be  a"^  carrier  in  1908.  Scheller^  re- 
ported thirty-two  cases  extending  over  a  period  of  fourteen 
years,  all  probably  due  to  a  carrier  who  had  been  sick  seven- 
teen years  before.  Gregg  *  found  a  woman  whose  blood  gave 
a  positive  Widal  reaction,  and  in  whose  feces  bacilli  were 
found,  and  who  had  had  typhoid  fever  fifty-two  years  before. 
She  had  presumably  infected  seven  persons.  Jundell's  case 
reported  below  was  infectious  perhaps  for  fifty-four  years. 
Chalmers's  case ''  had  had  the  disease  sixteen  years  before. 
Frosch ''  reports  that  evidence  was  presented  to  the  commis- 
sion appointed  by  the  Prussian  Government  to  study  this 
subject  as  follows:  That  fourteen  carriers  had  been  infective 
four  to  nine  years,  six  for  ten  to  twenty  years,  and  five  for 
from  twenty-one  to  thirty  years.  Soper's  case  has  now  been 
infectious  for  eight  years,  and  a  number  of  other  writers  report 
instances  of  carriers  who  were  presumably  excreting  bacilli 
more  or  less  constantly  for  periods  of  from  four  to  eight  years. 

1  Dean,  Brit.  M.  J.,  Lond.,  1908,  I,  562. 

2  Huggenberg,  Cor.-Bl.  f.  Schweiz.  Aerzte,  1908,  XXXVIII,  622. 

«  Scheller,   Centralbl.  f.  Bakteriol.  [etc.],  I,  Abt.  Orig.,  Jena,  1908, 
LXVI,  385. 

*  Gregg,  Boston  M.  &  S.  J.,  1908,  CLIX,  80. 

6  Chalmers,  Rep.  of  Med.  Off.  Health,  Glasgow,  1907,  61. 

6  Frosch,  Klin.  Jahrb.,  Jena,  1908,  XIX,  537. 


CARRIERS  AND  MISSED  CASES  33 

Tjrphoid  Bacilli  in  Persons  Never  Sick.  —  Not  only  are  per- 
sons who  have  had  typhoid  fever  often  found  to  be  "carriers  " 
of  the  germs,  but  persons  who  have  never  had  the  disease 
may  be  infected.  Allowance  must,  however,  be  made  for 
failure  to  recognize  and  remember  mild  atypical  attacks,  and 
some  of  the  chronic  carriers  who  are  said  never  to  have  been 
sick  may  have  forgotten  an  attack  of  "grip"  or  "malaria" 
years  before.  Soper's  case  so  far  as  known  had  never  had  the 
disease.  Houston's  case,  which  had  the  bacilli  in  the  urine 
for  three  years,  had  not  been  sick.  One  of  the  carriers,  the 
source  of  several  cases  discovered  by  Semple  and  Greig,  had 
never  had  typhoid  fever  so  far  as  known.  Roscoe  ^  reports 
an  outbreak  of  twelve  cases  in  an  insane  asylum  due  to  con- 
tact with  a  carrier  who  had  never  had  the  disease.  Jundell  ^ 
notes  a  series  of  twenty-two  cases  on  an  estate  in  Sweden 
occurring  at  intervals  since  1854.  The  grandmother  of  the 
family,  who  had  never  had  typhoid  fever,  was  shown  to  be 
excreting  the  bacilli  from  1904  until  the  time  of  the  report, 
1908. 

Carriers  among  Contacts.  —  Persons  brought  into  intimate 
relation  with  the  sick  may  become  infected  without  exhibit- 
ing any  symptoms  whatever.  Drigalski  and  Conradi  ^  found 
the  infection  in  4  healthy  persons  in  contact  with  typhoid 
cases.  Liefmann  and  Nieter^  found  7  carriers  out  of  252 
persons  examined  in  an  insane  asylum,  some  of  whom  it  was 
believed  were  carriers  and  the  causes  of  the  outbreak  in  the 
institution,  but  some  of  them,  however,  were  true  contacts. 
Scheller"  examined  40  persons  who  drank  the  milk  handled 
by  the  carrier  already  referred  to.  Of  these  5  were  sick,  and 
13  others,  who  had  no  symptoms  whatever,  were  yet  found 

»  Roscoe,  Lancet,  Lond.,  1909,  II,  1137. 
^  Jundell,  Abst.  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  388. 
'  Drigalski    and    Conradi,    Ztschr.    f.    Hyg.    u.    Infectionskrankh., 
Leipz.,  1902,  XXXIX,  283. 

*  Liefmann  and  Nieter,  Miinchen  mad.  Wchnschr.,  1906.  LIII,  2097. 
»  Griffith,  Med.  Press  &  Circ,  1905,  LXXIX,  208. 


34  THE  SOURCES  AND  MODES  OF  INFECTION 

to  be  excreting  typhoid  bacilli  in  either  feces  or  urine  or 
both.  All  of  them  became  free  from  germs  within  a  few 
weeks. 

Carriers  during  Incubation. —  Cler  and  Ferazzi^  during  a 
food  outbreak  of  typhoid  fever  found  that  6  of  39  persons  who 
had  eaten  the  food,  though  exhibiting  no  symptoms,  were 
carrying  the  bacilli  in  their  intestines.  These  "  temporary 
carriers  "  may  become  sick  later,  and  sometimes  the  period 
of  incubation,  so  called,  may  be  three  or  four  weeks  or  even 
longer.^  Indeed  it  is  not  rare  to  find  typhoid  bacilli  in  the 
feces  during  the  period  of  incubation.  During  the  Spanish 
War  typhoid  germs  were  found  in  the  feces  during  the  incu- 
bation period.^  Conradi  also  noticed  the  same  thing,  and 
considers  it  an  important  factor  in  the  spread  of  the  disease.* 
Ravenel  and  Smith  ^  have  reported  an  outbreak  of  forty  cases 
due  to  contact  with  a  case  before  the  symptoms  had  devel- 
oped. There  can  be  no  doubt  that  many  persons  are 
excreting  typhoid  bacilli  for  a  variable  time  while  they  are 
coming  down  with  the  disease,  that  from  fifteen  to  twenty- 
five  per  cent  continue  to  excrete  them  for  a  number  of 
weeks  after  recovery,  and  that  a  small  number  continue 
to  excrete  them  indefinitely  in  the  feces,  or  more  rarely 
in  the  urine.  These  chronic  cases  are  of  the  greatest 
importance  from  a  public  health  standpoint,  as  they  are  the 
least  likely  to  be  discovered  and  are  the  most  difficult  to 
control.  It  is  very  desirable  to  form  some  estimate  of  how 
numerous  they  are. 

Percentage  of  Carriers.  —  The  earliest  investigation  of  this 
subject  was  by  the  Germans.  Carriers  are  defined  by  Kut- 
scher  as  persons  in  whom  bacilli  persist  for  more  than  ten 

'  Cler  and  Ferazzi,  Centralbl.  f.  Bakteriol  [etc.],  Jena,  I  Abt.,  Ref. 
1905,  XXXVI,  479. 

'  Griffith,  Med.  Press  &  Circ,  1905,  LXXIX,  208. 

^  Abst.  of  Rep.  on  Origin  and  Spread  of  Typhoid  Fever  in  U  S. 
Military  Camps  during  Spanish  War  of  1898,  Wash.,  1900,  184. 

*  Conradi,  Deutsche  med.  Wchnschr.,  1907,  XXXIII,  1684. 

*  Ravenel  and  Smith,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1635. 


CARRIERS  AND   MISSED  CASES  35 

weeks  after  convalescence.  By  averaging  the  results  obtained 
by  Lentz,  Klinger  and  Drigalski,  it  appears  that  of  1982  cases 
of  typhoid  fever  53,  or  3  per  cent,  became  chronic  carriers.^ 
Park  ^  examined  the  feces  of  52  cases,  eight  months  after  re- 
covery and  found  bacilli  present  in  2;  in  one  of  them,  however, 
it  was  present  in  only  one  of  three  tests.  Of  16  other  persons 
who  had  the  disease  six  months  previously  2  were  carriers. 
He  thinks  that  two  per  cent  of  all  typhoid  fever  cases  become 
permanent  carriers,  and  these  ma}"  be  found  in  the  popula- 
tion at  the  rate  of  about  one  to  five  hundred.  Frosch  ^  gives 
a  tabulation  of  6708  cases  of  typhoid  fever,  of  which  310,  or 
4.62  per  cent,  continued  to  excrete  bacilli  for  over  ten  weeks, 
64  continued  carriers  for  from  three  months  to  one  year,  87 
for  one  to  three  years  and  15  for  three  and  one-half  years. 
Bruckner  *  states  that  of  316  persons  who  had  the  disease,  12, 
or  3.8  per  cent,  became  carriers,  or,  omitting  the  104  children, 
only  1  of  whom  was  a  carrier,  and  who  rarely  become  such, 
5.2  per  cent  continued  to  excrete  bacilli.  Recently  Hamilton," 
following  the  suggestion  of  Gaehtens,  tested  the  opsonic  index 
of  25  persons  who  had  gall-bladder  trouble  and  found  7  with 
an  abnormally  high  index.  All  7  proved  to  be  carriers.  She 
hopes  that  this  will  prove  a  simple  means  of  discovering 
carriers. 

Carriers  among  the  Public.  —  There  have  been  a  few 
studies  to  deterinino  the  number  of  carriers  in  the  general 
population.  Minelli  ^  found  1  carrier  in  250  prisoners  in 
Strasburg.  The  most  extensive  investigation  has  recently 
been  carried  on  in  Washington,^  where  the  feces  from  986 

>  U.S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. No. 35,  169. 
2  Park,  J.  Am.  M.  Ass.,  Chicago,  1908,  LI,  981. 
'  Frosch,  Klin.  Jahrb.,  Jena,  1908,  XIX,  537. 

*  Briickner,  Arb.  a.  d.  k.  Gesundhtsamte.,  Berl.,  1910,  XXXIII,  435. 

*  Hamilton,  J.  Am.  M.  Ass.,  1910,  LIV,  704. 

*  Minelli,  Centralbl.  f.  Bakteriol.  [etc.],  Jena,  I  Abt.  Orig.,  1906, 
XLI,  406. 

'  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull.  No.  52, 
13.  145. 


36  THE  SOURCES  AND  MODES  OF  INFECTION 

well  persons  were  examined  bacteriologically.  Only  one 
test  was  made  for  each  person,  and  3  carriers  were  found. 
These  were  subsequently  re-examined  and  2  proved  to  be 
negative. 

Intermittent  Excretion. — It  seems  probable  that  the  num- 
ber of  carriers  is  really  larger  than  the  above  figures  indicate. 
There  is  no  doubt  that  many  carriers  do  not  excrete  bacilli 
continuously.  Davies  and  Hall  ^  called  attention  to  the 
marked  intermittency  of  bacillus  excretion  in  their  case,  re- 
ported previously  by  Davies,  and  which  will  be  again  referred 
to.  This  patient  had  been  infectious  at  times  for  four  years, 
particularly  in  the  spring,  and  on  one  occasion  she  was  her- 
self sick.  Semple  and  Greig  report  several  instructive  cases. 
One  of  their  cases  gave  only  negative  tests  for  thirty-one  days, 
followed  by  a  positive;  another  carrier  remained  free  from 
bacilli,  as  shown  by  daily  examination,  for  a  period  of  seventy- 
five  days,  and  other  cases  for  lesser  periods.  Scheller  noted 
considerable  intermittency  in  the  excretion  of  bacilli.  Of  108 
examinations  of  urine  and  feces  from  18  carriers,  only  48 
were  positive.  This  intermittency,  coupled  with  the  difficulty 
of  finding  the  bacillus  when  it  is  certainly  present,  renders  it 
probable  that  carriers  are  frequently  overlooked,  and  makes 
it  extremely  difficult  to  apply  bacteriological  examinations  in 
public  health  work. 

Carriers  Cause  Disease. — That  these  carriers  can  be  the 
source  of  disease  in  others  has  been  amply  demonstrated. 
When  I  began  to  write  this  chapter  nearly  three  years  ago,  I 
was  intending  to  include  references  to  all  outbreaks  reported 
as  due  to  carriers,  but  such  reports  are  now  so  frequent  that 
this  is  scarcely  possible.  A  good  resume  of  previous  literature 
may  be  found  in  the  United  States  Public  Health  and  Marine 
Hospital  Service  Bulletin  35.  A  number  of  additional  in- 
stances of  infection  by  carriers  have  already  been  noted. 
Among  the  most  interesting  and  well  known  of  these  is  that 

1  Davies  and  Hall,  Lancet,  Lond.,  1908,  II,  1585. 


CARRIERS  AND  MISSED  CASES  37 

reported  by  Soper '  of  a  cook  who  infected  twenty-six  persons, 
living  in  six  families  residing  in  five  localities,  in  three  states. 
The  infections  took  place  between  1901  and  1906.  The  cook 
gave  no  history  of  having  had  typhoid  fever,  but  her  feces 
were  swarming  with  bacilli.  She  was  then  placed  in  isolation 
in  a  contagious  hospital.  In  1908  an  attempt  was  made  in 
the  courts  to  secure  the  release  of  "  Typhoid  Mary  "  as  she 
is  called,  but  it  was  unsuccessful.  What  result  is  secured  by 
keeping  her  in  confinement,  other  than  the  placing  of  dis- 
credit on  public  health  work,  it  is  difficult  to  see. 

Milk  and  Contact.  —  The  handling  of  milk  by  carriers  is 
especially  dangerous  to  the  public.  Kayser,  Cameron,'  Schel- 
ler,  Chalmers,  Davies,  Lumsden  and  Woodward,^  Albert* 
and  others  have  reported  outbreaks  due  to  milk  infected  in 
this  way.  In  the  case  reported  by  Albert  the  bacilli  were  in 
the  urine  of  a  milker  who  had  been  sick  a  year  before.  In- 
stances of  contact  infection  in  insane  asylums  have  been 
reported  by  Nieter  and  Liefmann,  Levy  and  Kayser,  Friedel, 
Dehler,  C.  Neisser  ^  and  Ledingham."  Dehler  '  removed  the 
gall  bladder  from  two  carriers  who  were  found  to  be  the 
cause  of  the  outbreak,  and  their  feces  were  afterwards  free 
from  bacilli.  Loele,^  however,  opened  the  gall  bladder  in  a 
convalescent  typhoid  case  which  was  excreting  bacilli,  l)ut  no 
trace  of  thorn  could  be  found  in  the  gall  bladder. 

Carrier  at  Bristol.  —  A  very  interesting  case  is  reported  by 
Davies,^  of  Bristol,  England.  A  woman  had  typhoid  fever 
in  1901.  In  1904  she  Ijecame  the  cause  of  a  severe  outbreak 
in  a  girls'  school,  and  in  1907  of  another  outbreak  in  another 

»  Soper,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  2019. 

2  Cameron,  Pul).  Health,  Lond.,  1909,  XXII,  243. 

'  Lum.sdcn  and  Woodward,  J.  .\m.  M.  .\.ss.,  Chicago,  1909,  LII,  749. 

«  Albert,  Am.  J.  Pul).  Ilyg.,  1909,  XIX,  2()0. 

»  C.  Neisser,  Psychiat.-neurol.  Wchnschr.,  Halle,  1908-9,  X,  37. 

«  Ledingham,  Brit.  M.  J.,  Lond.,  1908,  I,  15. 

'  Dehler,  Miincih.  med.  Wchnschr.,  1907,  LIV,  779,  2134. 

'  Loele,  Deutsche  med.  Wchn.schr.,  1909,  XXXV,  1429. 

"  Davies,  Pioc.  Roy.  Soc.  Med.,  1908,  I,  Epidemiol.  Sec,  224. 


38  THE  SOURCES  AND  MODES  OF  INFECTION  ' 

institution  where  she  handled  the  milk  which  was  proved  to 
be  the  vehicle  of  infection.  It  is  noteworthy  that  of  seven 
examinations  of  the  feces  of  this  carrier,  in  five  no  bacilli 
were  found;  and  of  these,  four  were  successive,  from  January 
20  to  March  14.  This  indicates  that  negative  results  from 
such  examinations  are  of  little  value. 

The  Spanish  War  investigation  showed  that  most  of  the 
volunteer  regiments  were  infected  when  they  came  to  camp, 
that  is,  they  must  have  contained  carriers  or  mild  cases,  and 
it  was  by  extension  from  these  that  most  of  the  true  typhoid 
fever  later  developed.^  The  distinction  between  a  case  of 
true  typhoid  fever  of  mild  type  and  a  carrier  often  cannot  in 
practice  be  made.  There  is  no  sharp  line  of  demarcation, 
but  infection  by  typhoid  bacilli  may  result  in  a  series  of  cases 
presenting  gradation  from  the  most  severe  symptoms  to  none 
at  all.  It  is  most  unwarranted  to  assume,  as  some  appear  to 
do,  that  a  mild  unrecognized  walking  typhoid  case  may  start 
up  an  outbreak,  but  that  a  true  carrier  cannot  do  so. 

Atypical  Typhoid  Fever.  —  There  can  be  no  question  that 
mild  unrecognized  cases  of  typhoid  fever  are  extremely  com- 
mon. Greater  care  in  diagnosis  has  made  an  apparent  increase 
in  the  number  of  reported  cases  of  this  disease,  and  a  decrease 
in  the  fatality.  Thus  in  my  own  city  the  reported  fatality  from 
typhoid  fever  has  during  the  last  twenty  years  been  reduced 
from  50  to  12  per  cent;  and  it  is  probably  really  considerably 
less  than  that.  I  have  noticed  that  in  milk  and  water  out- 
breaks, when  public  attention  is  directed  strongly  towards 
the  disease,  the  case  fatality  is  often  very  low,  which  merely 
means  that  most  of  the  cases  have  been  recognized.  In  the 
Spanish  War  the  committee  of  investigation  believed  that  the 
number  of  cases  actually  existing  amounted  to  20,738,  while 
the  number  reported  by  the  army  surgeons  was  only  10,428. 

Recently  Bates  "  has  reported  a  series  of  mild  atypical 

1  Abstr.  of  Rep.  on  the  Origin  and  Spread  of  Typhoid  Fever  during 
the  Spanish  War  of  1898,  Wash.,  1900,  168-175. 

2  Bates,  J.  Am.  M.  Ass.,  Chicago,  1908,  L,  585. 


CARRIERS  AND  MISSED  CASES  39 

typhoid  fever  cases  in  Panama  Canal  Zone,  and  states  that 
such  cases  are  quite  common  there,  and  are  the  chief  factor 
in  the  extension  of  the  disease.  At  the  time  Koch  made  his 
investigation  of  the  four  Trier  villages  there  were  8  recognized 
cases,  but  a  thorough  bacteriological  investigation  of  sus- 
pects discovered  64  more.  Of  these  49  were  children.^  These 
mild  unsuspected  walking  typhoid  cases  not  rarely  result  in 
death.  Velich "  notes  36  such  cases,  and  a  number  of  others 
are  reported  by  Curschmann,  and  they  also  have  been  seen 
by  the  writer.  I  have  recently  investigated  two  milk  out- 
breaks, in  one  of  which  the  cause  was  apparently  a  mild  un- 
recognized case,  and  in  the  other  either  a  convalescent  or  a 
carrier  associated  with  him.  Neufeld  ^  devotes  considerable 
space  to  this  class  of  cases. 

Paratyphoid.  —  Rimpeau  *  found  paratyphoid  bacilli  in  3 
of  50  healthy  school  children,  and  in  1  of  50  orphans.  Only 
one  examination  of  the  feces  was  made.  Savage,''  who  has 
devoted  much  attention  to  the  distribution  of  this  bacillus, 
did  not  find  it  in  12  healthy  persons.  He  believes  that  the 
disease  does  not  spread  among  human  beings  like  typhoid 
fever,  but  is  usually  derived  from  the  lower  animals  by  the 
ingestion  of  infected  food. 

Cholera  Spirilla  in  Convalescents.  —  According  to  Kolle,^ 
cholera  spirilla  are  sometimes  found  in  the  intestines  of  con- 
valescents as  long  as  48  days.  Rommelaere  ^  reported  a  case 
retaining  the  infection  47  days.  Forrest  *  found  the  germs 
remaining  6  weeks.  Kirchner^  says  that  the  spirilla  are  some- 
times carried  for  weeks  or  months.    Most  observers,  however, 

*  Koch,  Die  Bekampfung  des  Typhus,  Berl.,  1893,  14-15. 

'  Velich,  Arch.  f.  Hyg.,  Miinohen  u.  Leipz.,  1904,  XLIX,  113. 

*  KoUe  u.  Wasscrmann,  Handhuch  [otc],  Jena,  1903,  II,  271. 

*  Rimpeau,  Deutsche  med.  Wchnschr.,  1908,  XXIV,  1045. 

»  Rep.  Med.  Off.  Local.  Gov.  Hd.,  Lond.,  1908-09,  XXXVIII,  316. 
"  KoUe,  Ztsclir.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1895,  XVIII. 
^  Rommelaere,  J.  de  med.,  Brux.,  1S92,  XCIV,  837. 
"  Forrest.  J.  Trop.  M.  [etc.],  Lend.,  1908,  XI,  321. 

*  Kirchner,  Klin.  Jahrb.,  Jena,  1908,  XIX,  473. 


40  THE  SOURCES  AND  MODES  OF  INFECTION 

find  that  they  disappear  in  a  few  days.  Pfeiffer^  reviews  the 
literature,  and  cites  Simond's  observation  that  the  average 
duration  of  infection  is  only  about  6  days,  and  that  the 
longest  seen  by  him  was  18  days.  Of  117  cases  reported 
to  Rumpel  not  one  carried  the  germs  over  24  days.  Abel  and 
Claussen  found  the  average  of  17  cases  to  l^e  5  or  6  days,  and 
Pfeiffer  the  average  of  39  cases  10  days,  though  in  2  the  infec- 
tion persisted  23  days.  Other  writers  have  made  similar 
observations. 

Spirilla  in  Healthy  Persons.  —  Dunbar  -  was  the  first  to 
note  the  occurrence  of  cholera  spirilla  in  the  feces  of  healthy 
persons.  He  discovered  28  healthy  carriers  in  Hamburg 
in  1892-93.  Rommelaere  noted  such  a  carrier  in  1892,  and 
carriers  are  by  Koch  considered  an  important  factor  in 
the  spread  of  the  disease.  In  1905  cholera  seemed  to  have 
been  brought  down  the  rivers  from  Russia  into  Germany 
by  raftsmen,  and  Kirchner  says  that  of  27  persons  on  one 
raft  2  were  carriers.  Pfeiffer  states  that  in  this  outbreak 
there  were  174  cases  of  the  disease,  and  that  38  other  carriers 
were  discovered.  He  cites  Frosch  as  discovering  16  carriers, 
of  whom  12  were  children,  and  Friedheim  as  finding  51.  In 
one  family  observed  by  Pfeiffer  4  died,  1  was  very  sick,  1 
was  mildly  sick,  and  2  were  carriers.  He  says  that  there  are 
very  many  mild  cases  of  the  disease  which  can  only  be  recog- 
nized bacteriologically.  McLaughlin^  found  17,  or  6.44  per 
cent  of  264  prisoners  in  Manila,  to  be  carriers,  and  in  the  city 
27,  or  7.18  per  cent  of  376  persons  examined.  Gotschlich* 
examined  pilgrims  returning  from  Mecca,  and  though  cholera 
had  not  so  far  as  known  prevailed  among  them,  he  found 
several  Russian  and  Turkish  pilgrims  who  proved  to  be  car- 
riers of  the  spirilla.     According  to  Pfeiffer  these  spirilla  of 

'  Pfeiffer,  Klin.  Jahrb.,  Jena,  1908,  XIX,  483. 
'  Dunbar,  Mod.  Med.,  Osier,  Phila.  &  N.  Y.,  1907,  II,  720. 
'  McLaughlin,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIT,  1155. 
*  Gotschlich,   Ztschr.  f.  Hyg.  u.   Infectionskrankh.,  Leipz.,   1906, 
LIII,  281. 


CARRIERS  AND   MISSED  CASES  41 

Gotschlich  have  been  carefully  studied  by  a  number  of  ob- 
servers and  show  slight  variations  from  the  type,  and  have 
probably  lost  their  virulence.  Yakovlew,  Zabolotny,  Zlato- 
goreff  and  Koulecha  '  state  that  in  St.  Petersburg  the  feces 
from  2440  apparently  well  persons  were  examined,  all  of 
whom  had  been  more  or  less  in  contact  with  cholera  cases. 
Of  these  125  contained  the  cholera  spirillum,  of  which  40 
were  from  what  proved  to  be  mild  unrecognized  cases,  25 
from  persons  who  were  incubating  the  disease,  and  60  were 
from  true  carriers.  Pfeiffer  reports  several  instances  in  which 
the  disease  was  spread  by  carriers. 

Chronic  Plague  in  Rats.  —  Bubonic  plague  is  a  disease 
which  attacks  not  man  alone  but  many  other  species  of  ani- 
mals, particularly  the  rat.  In  fact  it  may  be  considered 
primarily  a  rat  disease,  and  without  doubt  the  rat  is  the  most 
important  agent  in  its  diffusion.  That  mild  cases  and  chronic 
cases  exist  among  rats  which  superficially  appear  not  to  be 
sick,  seems  to  be  proved.  Simpson  ^  saj's  chronic  plague  was 
observed  in  some  of  the  animals  experimented  on  in  Hong 
Kong,  and  by  Albrecht  and  Ghon  in  experimental  guinea 
pigs,  and  in  rats  for  months  by  Kolle  and  Martini.  The 
Indian  Plague  Commission  (1905)^  found  eleven  of  the  rats 
which  they  had  fed  with  plague  bacilli  to  be  infected,  although 
they  appeared  to  be  perfectly  well.  While  chronic  plague  has 
been  seen  in  laboratory  animals,  several  observers  in  Bom- 
bay and  Sj^dney  have  failed  to  find  it  under  natural  condi- 
tions, as  also  did  Blue  in  San  Francisco.*  But  Hunter  found 
rats  with  chronic  plague  in  Hong  Kong,  and  the  Indian 
Plague  Commission  (1905)  found  a  number  of  rats  infected 
with  plague  at  a  time  when  no  rats  with  acute  plague  could 
be  discovered,  and  when  there  was  no  outbreak  among  human 

'  Yakovlew,  Zabolotny,  Zlatogoreff  and  Koulecha,  Bull.  Soc.  path, 
exot.,  Par.,  1909,  II,  276. 

*  Simpson,  A  Treatise  on  PlaRuo,   Cambridge,  1905,  129. 
'  J.  Hyg.,  Cambridge,  1907,  VII,  379. 

*  Blue,  J.  Hyg.,  Cambridge,  1909,  IX,  1. 


42  THE  SOURCES  AND  MODES  OF  INFECTION 

beings.  The  infected  rats  showed  no  sign  of  sickness.^  Wat- 
kins-Pitchford  "  found  the  bacillus  in  convalescent  rats  and 
guinea  pigs.  It  is  evident  that  such  chronic  "  carriers"  may 
be  an  important  factor  in  the  maintenance  and  extension  of 
the  disease. 

Atypical  Hirnian  Plague.  —  Among  human  beings  mild 
cases  of  the  glandular  type  are  by  no  means  uncommon. 
But  fortunately  these  are  rarely  dangerous,  for  without 
suppuration  there  is  no  escape  of  bacilli.  But  in  certain  in- 
stances, later  suppuration  may  take  place,  or  lung  symp- 
toms develop,  so  that  the  individual  may  become  a  focus  of 
infection.^  Rat  "carriers,"  on  the  other  hand,  are  always 
dangerous,  for  they  may  at  any  time  suffer  accidental  death, 
and  their  carcasses  may  then  readily  infect  other  animals 
and  even  man. 

Plague  Bacilli  in  Convalescents.  —  In  the  pneumonic  type 
in  human  beings  the  bacilli  are  thrown  off  in  large  numbers 
from  the  lungs.  Martin,^  Gotschlich  ^  and  others  have  found 
them  in  the  sputum  up  to  76  days  after  the  attack,  or  42 
days  after  recovery.  Gaffky"  cites  Vagedes  as  reporting 
pulmonary  infection  lasting  2  months  in  a  case  in  Oporto,  and 
bacilli  in  an  abscess  persisting  more  than  2  months,  and  Vages 
one  lasting  4  weeks  in  Paraguay.  The  latter  also  isolated  the 
bacilli  from  a  man  who  later  became  sick  with  the  disease. 
Shottelius  found  the  germs  in  the  bronchial  secretion  of  mild 
ambulant  cases.  It  is  thus  very  probable  that  mild  cases 
and  true  carriers  among  both  rats  and  human  beings  may 
play  a  considerable  part  in  the  dissemination  of  this  disease. 

'  J.  Hyg.,  Cambridge,  1906,  VI,  530-535;   1907,  VII,  373. 

^  Watkins-Pitchford,  Rep.  of  Bacteriologist,  Pietermaritzburg,  Natal, 
1903  [Rep.  on  Plague,  31]. 

3  Gotschlich,  Kolle  u.  Wassermann,  Handbuch,  Jena  [etc.],  1904, 
IV',  69. 

*  Martin,  Ann.  de  I'lnst.  Pasteur,  Par.,  1900. 

^  Gotschlich,  Ztschr.  f.  Hyg.  Infectionskrankh.,Leipz.,  1899,  XXXII, 
402. 

"  Gaflfky,  Klin.  Jahrb.,  Jena,  1908,  XIX,  491. 


CARRIERS  AND  MISSED  CASES  43 

Bacillary  Dysentery.  —  There  are  two  forms  of  dysentery, 
one  caused  by  a  bacillus,  the  other  by  an  ameba.  Collins'  and 
Goodwin^  have  studied  the  occurrence  of  the  bacillus  in  well 
persons.  According  to  Collins,  Flexner,  Wollstein  and  others 
failed  to  find  it  in  healthy  persons.  DuvaP  found  it  in 
2  instances,  and  Charlton  and  Jehle*  in  2  of  10  cases  exam- 
ined. Collins  found  it  in  2  of  30  normal  persons,  and  in  1 
three  weeks  after  an  attack  of  dysenterj^,  and  in  another  child 
who  had  had  a  few  mucous  stools.  Goodwin  found  the  Flex- 
ner-Manila  type  of  the  bacillus  in  1  of  59  well  persons  exam- 
ined. Kruse  ^  says  that  all  types  of  the  bacilli  have  been 
found  in  well  persons  and  that  these  carriers  are  an  important 
cause  of  the  disease.  Though  carriers  have  fewer  bacilli  in 
their  feces,  which  are  also  less  in  volume,  they  come  in  con- 
tact with  a  larger  number  of  persons  than  do  the  sick.  There 
are  also  many  mild  atypical  cases.  Kruse  has  found  the 
bacilli  in  relapses  after  two  years,"  and  says  that  Drigalski 
and  Lentz  have  made  similar  observations.  He  also  cites 
Ford  as  finding  10  carriers  among  50  persons  examined.  In 
an  asylum  outbreak  Heuser  ^  found  3  carriers.  Conradi,' 
while  studying  a  contact  outbreak  near  Metz,  found  several 
carriers.  Kiister  ^  isolated  bacilli  from  a  carrier  who  had 
probably  been  excreting  since  an  attack  years  before.  Kruse 
cites  Kriege  as  saying  that  about  4  of  36  cases  of  dysentery 
become  chronic,  but  usually  the  infection  lasts  only  2  to  6 
weeks.  Conradi  found  that  in  4  of  27  cases  the  bacilli  per- 
sisted up  to  the  end  of  the  fourth  week,  while  in  1 1  cases  they 

»  Collins,  Rep.  Dopt.  Health,  City  of  New  York,  1904,  I,  428. 

»  Goodwin,  Rep.  Dept.  Health,  City  of  New  York,  1904,  I,  423. 

»  Duval,  Studies  from  Rockefeller  Inst.,  1904,  II,  42. 

*  Charlton  and  Jehle,  Tr.  Ass.  Am.  Physicians,  1904,  XIX,  405. 

»  Kruse,  Med.  Press  &  Circ,  1908,  LXXXV,  175. 

»  Kruse,  Klin.  .Jahrb.,  .Jena,  1908,  XIX,  529. 

^  Heuser,  Deutsche  raed.  Wchn.schr.,  1909,  XXXV,  1694. 

'  Conradi,  Festschrift  v.  Robert  Koch,  1903,  555. 

■  Kiiflter,  Miinchen  med.  Wchnschr.,  1908,  LV,  1833. 


44  THE  SOURCES  AND  MODES  OF  INFECTION 

disappeared  by  the  middle  of  the  second  week.  Shiga  ^  says 
that  the  bacilh  generally  remain  1  or  2  weeks,  and  that 
perfectly  normal  persons  sometimes  harbor  the  germs.  Ave- 
line,  Boycott  and  McDonald^  failed  to  find  the  bacillus  in  27 
contacts  in  an  asylmn. 

Mediterranean  Fever. — Mediterranean  fever,  like  plague, 
appears  to  be  a  disease  of  the  lower  animals,  only  secondarily 
affecting  man.  The  germ  which  is  its  cause  may,  like  so 
many  other  pathogenic  organisms,  develop  in  the  body  with- 
out giving  rise  to  symptoms.  Goats  appear  to  be  the  chief 
source  of  human  infection.  In  1905  there  were  363  cases 
among  the  garrison  at  Malta,  but  in  1906,  presumably  owing 
to  the  cutting  off  of  the  supply  of  goat  milk,  there  were  only 
35  cases;  ^  and  in  1907  it  was  practically  exterminated.*  An 
interesting  account  is  given  of  an  outbreak  of  the  disease  on 
a  steamship,  among  persons  who  drank  the  milk  of  a  herd  of 
goats  that  were  being  brought  to  America."  The  goats  were 
not  sick.  Horrocks**  shows  that  probably  one  or  more  ani- 
mals in  every  herd  are  excreting  the  germs  in  the  milk  and 
urine,  and  that  50  per  cent  give  evidence  by  serum  reaction 
that  they  are,  or  have  been,  infected.  Other  investigations 
show  that  as  high  as  10  per  cent  of  milch  goats  have  the  germs 
in  their  milk,  although  they  present  no  symptoms  of  the 
disease.  Carriers  are  also  common  among  human  beings. 
Shaw  ^  found  that  10  of  525  well  persons  were  excreting  the 
germs  in  the  urine. 

Meningococcus  in  Nose.  —  While  the  germ  of  epidemic 
cerebro-spinal  meningitis  (Micrococcus  meningitidis)  has  been 

'  Shiga,  Philippine  J.  Sc,  Manila,  1906,  I,  485. 

2  Aveline,  Boycott  and  McDonald,  J.  Hyg.,  Cambridge,  1908,  VIII, 
309. 

3  Hewlett,  Practitioner  (Lond.),  1908,  LXXX,  222. 
*  Bruce,  Nature,  Lond.,  1908,  LXXVIII,  39. 

'  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull.  No.  41, 
203. 

°  Horrocks,  Rep.  of  Commission  of  Roy.  Soc,  1905-6,  Pts.  Ill,  IV. 
'  Shaw,  J.  Roy.  Army  Med.  Corps,  Lond.,  1906,  VI,  638. 


CARRIERS  AND  MISSED  CASES  45 

known  for  many  years,  it  is  only  very  recently  that  any  ex- 
planation has  been  forthcoming  as  to  the  mode  of  infection. 
The  finding  of  the  organism  in  the  nose  of  patients  suggests 
the  possibility  that  infection  may  pass  to  the  brain  from  this 
point.  It  is  theoretically  possible  for  infection  to  take  place 
through  the  cribriform  plate  of  the  ethmoid  bone,  or,  as  sug- 
gested l)y  Westenhoeffer,^  by  the  lymphatics  from  the  pha- 
ryngeal tonsils,  or  as  some  think,  by  absorption  from  the 
alimentary  canal  and  passage  through  the  lymph  channels  or 
the  general  circulation.  The  organism  is  certainl}^  found  in 
the  blood  in  a  considerable  number  of  cases.'  What  the  exact 
route  to  the  brain  is,  however,  has  not  yet  been  determined. 

That  the  germ  of  this  disease  is  found  in  the  nose  of  the 
sick  is  now  generally  recognized,  though  considerable  doubt 
has  been  throwTi  on  the  accuracy  of  some  of  the  earlier  obser- 
vations, as  this  organism  is  not  readily  distinguished  from 
the  cocci  frequently  found  in  the  normal  nose.  Culture  and 
agglutination  tests  are  now  recognized  as  the  only  valid 
methods  of  differentiation.  Among  those  who  have  certainly 
isolated  it  in  a  considerable  number  of  instances  from  the 
nasal  mucous  membrane  of  cerebro-spinal  meningitis  cases 
may  be  mentioned  Dunham,^  Weichselbaum  and  Gohn,*  Lin- 
gelsheim,'^  Goodwin  and  von  Sholly  ^  and  others. 

Causes  Rhinitis. — That  this  micrococcus  is  frequently  found 
in  the  nose  of  contacts,  and  other  persons  showing  no  symp- 
toms of  the  disease,  is  now  well  established.  An  interesting 
case  is  that  of  Kiefer,'^  who  while  working  with  a  culture  in 
the  laboratory  developed  a  severe  rhinitis  and  succeeded  in 

»  Westenhoeffer,  Berl.  klin.  Wchnschr.,  1905,  XLII,  737. 

^  Birnio  and  Smith,  Am.  J.  M.  Sc,  Phila.,  1907,  CXXXIV,  582,  and 
Simon,  J.  Am.  M.  A.ss.,  Chicago,  1907,  XLVIII,  1938. 

»  Dunham,  J.  Infoct.  Dis.,  Chicago,  190G  [Suppl.  No.  2],  10. 

*  Wcichs(>ll)auman(l  Gohn,  Wien.  klin.  Wchnschr.,  1905,  XVIII,  025. 

'  Lingolsheim,  Klin.  Jahrb.,  Jena,  1906,  XV,  373. 

"  Goodwin  and  von  Sholly,  J.  Infect.  Dis.,  Cliicago,  190G  [Suppl. 
No.  2],  21. 

'  Kiefer,  Berl.  klin.  Wchnschr.,  190G,  XXXIII,  G28. 


46  THE  SOURCES  AND  MODES  OF  INFECTION 

recovering  the  micrococcus  from  his  nose.  A  similar  case  was 
reported  to  me  by  P.  E.  Rauschenbach,  at  the  time  working 
in  a  hospital  at  Newark.  ForcU  also  had  a  case  of  this  kind. 
Meningococcus  in  Contacts.  —  Among  those  who  have 
found  the  organism  in  well  persons  may  be  mentioned  Weich- 
selbaum  and  Gohn,^  who  obtained  it  in  3  of  24  persons  exam- 
ined, Ostermann^  found  it  in  17  of  24  contacts  in  Breslau, 
but  his  methods  of  employing  the  agglutination  test  have 
been  called  in  question.  One  well  child  in  whose  nose  the 
germs  were  found  was  taken  sick, three  days  later  and  died 
the  next.  day.  Many  of  the  carriers  had  pharyngitis  and 
rhinitis.  Of  49  children  in  schools  where  these  carriers  at- 
tended, 2  showed  the  meningococcus,  and  one  of  these  had 
been  playing  with  a  carrier.  Ostermann  failed  to  find  it  in 
50  persons  who  had  not  come  in  contact  with  cerebro-spinal 
cases.  Goodwin  and  von  Sholly,  in  New  York,  obtained  it 
in  5  of  45  contacts,  and  a  similar  coccus  which  did  not  agglu- 
tinate, in  2  of  55  medical  students  not  contacts.  Bolduan" 
found  the  organism  in  10  per  cent  of  150  contacts.  Lingels- 
heim,^  during  an  extensive  outbreak  in  Beulen,  Prussia,  found 
the  organism  in  the  nose  of  26,  or  9  per  cent  of  289  contacts. 
Later  he  found  it  in  4  of  56  school  children, but  all  4  came  from 
families  where  there  had  been  cases  of  the  disease.  In  2  of 
the  4  cases  no  agglutination  test  was  applied.  In  the  cases 
of  the  disease  examined  by  Lingelsheim  the  micrococcus  dis- 
appeared by  the  fifth  day  in  66  per  cent,  and  by  the  sixth  to 
tenth  day  in  24  per  cent.  In  4.39  per  cent  of  the  cases  it  per- 
sisted over  three  weeks,  and  in  1  case  it  was  found  three 
months  from  the  beginning  of  the  attack. 

1  Quoted  by  Councilman,  J.  Am.  M.  Ass.,  1905,  XLIV,  999. 

2  Weichselbaum  and  Gohn,  Wien.  klin.  Wchnschr.,   1905,  XVIII, 
625. 

3  Ostermann,  Deutsche  med.  Wchnschr.,  1906,  XXXII,  414. 
'  Bolduan,  Med.  Times,  N.  Y.,  1908,  XXXVI,  193. 

'  Lingelsheim,  Deutsche  med.  Wchnschr.,  1905,  XXXI,  1017,  1217; 
Klin.  Jahrb.,  Jena,  1908,  XIX,  519. 


CARRIERS  AND  MISSED  CASES 


47 


Infection  in  the  Family. —  Bruns  and  Hohn^  found  that  the 
proportion  of  carriers  decreased  as  the  outbreak  decreased. 
This  is  shown  in  the  following  table: 


March . 
April .  . 
May .  . 
June. . 
July.. 
August 


Reported 
Cases. 

No.  of 
Families 

No.  of  Well 

i'er>ons 
Examined. 

No.  of 
Carriers. 

148 

278 
327 
188 
146 
68 

7 
39 
42 
23 
21 
22 

23 

135 

172 

93 

67 

119 

14 

67 
81 
34 
18 
10 

Per  cent  of 
Carriers. 


61 
50 

47 
36 
27 

8.5 


They  found  that  of  the  fathers  in  these  families  60  of  113 
carried  the  germs;  of  the  mothers,  39  of  114;  of  children  in  the 
families,  118  of  360;  and  of  other  members  of  the  families 
7  of  22  were  carriers. 

Persistence  of  Infection.  —  Bruns  and  Hohn  give  for  the 
duration  of  the  infection  the  following: 


For  8  days 28  cases 

2  weeks 18  cases 

3  weeks 13  cases 

4  weeks 10  cases 


For  5  weeks 4  cases 

6  weeks 3  cases 

7  weeks 3  cases 

8  weeks 1  case 


Selter,  in  Bonn,-  has  observed  a  very  much  longer  persist- 
ence of  the  infection.  In  the  case  of  a  mother  and  daughter 
who  recovered  from  the  disease,  the  cocci  persisted  from 
February  3  to  June  4.  The  father  in  this  family,  who 
had  not  been  sick,  yielded  positive  findings  in  May,  June, 
July  and  August,  and  had  in  all  probability  been  infective 
for  seven  months.  In  another  family  where  the  disease  ap- 
peared, the  6  well  persons  were  carriers  at  one  time  or 
another  from  February  18  to  June  5,  during  which  period 

1  Bruns  and  Hohn,  Klin.  Jahrb.,  Jena,  1907-08,  XVIII,  285. 
»  Seltcr,  Klin.  Jahrb.,  Jena,  1908-09,  XX,  457. 


48  THE  SOURCES  AND  MODES  OF  INFECTION 

they  were  examined  twelve  times.  Sometimes  the  examina- 
tions were  positive  and  sometimes  negative,  which  is  just 
what  occurs  in  the  examination  of  typhoid  and  diphtheria 
carriers.  This  apparent  intermittency  may  be  due  in  part 
to  faulty  technique,  and  in  part  to  the  temporary  absence 
of  the  bacteria.  In  the  69  examinations  of  the  family 
above  referred  to,  49  were  positive  and  20  negative.  Selter 
could  find  no  difference  between  the  cocci  found  in  the 
sick  and  in  the  carriers,  but  he  was  not  able  to  trace  a 
case  of  sickness  to  any  of  his  known  carriers.  Kirchner,^ 
in  Hamburg,  found  22,  or  9.7  per  cent,  carriers,  out  of  237  well 
members  of  infected  families,  but  in  3  families  all  the  mem- 
bers were  carriers,  and  in  10  other  families  75  per  cent  were. 
Most  of  these  were  adults.  In  two  instances  the  infection 
persisted  44  and  66  days  respectively.  Vagedes  ^  reports  3 
cases  in  barracks  at  Charlottenburg.  Of  58  hospital  attend- 
ants, etc.,  there,  4  were  carriers,  and  of  593  of  the  soldiers  10 
only  were  carriers.  On  a  second  examination  five  days  later 
1  only  was  found,  and  nineteen  days  later  none.  By  the  iso- 
lation of  carriers  the  disease  was  "  stamped  out,"  but  it  will 
be  noticed  that  the  infection  was  not  widely  diffused  before  it 
was  recognized.  Bochalli,^  in  certain  barracks  where  the 
disease  prevailed,  found  10  of  16  roommates  of  the  sick,  or 
62  per  cent,  to  be  carriers.  Of  485  in  other  companies,  42,  or 
8.6  per  cent,  were  infected.  Usually  the  germs  quickly  dis- 
appeared, but  in  one  case  they  persisted  for  four  and  a  half 
months.  In  another  instance  a  nurse,  going  to  a  district 
where  there  was  no  meningitis,  was  attacked  about  one  month 
later.  Similar  observations  have  been  made  in  several  places 
during  the  recent  outbreak  in  Scotland.  Buchanan,*  in  Glas- 
gow, found  the  micrococcus  in  81,  or  26.3  per  cent  of  308  con- 

1  Kirchner,  Klin.  Jahrb.,  Jena,  1908,  XIX,  473. 
^  Vagedes,  Deutsche  mil.-iirztl.  Ztschr.,  Berl.,  1907,  XXIII,  647. 
^  Bochalli,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1908,  LXI, 
454. 

*  Buchanan,  San.  Rec,  Lond.,  1907  n.  s.,  XI,  245. 


CARRIERS  AND  MISSED  CASES  49 

tacts  in  74  families.  Most  of  them  were  over  fifteen  years  of 
age.  In  14  families  he  obtained  it  from  more  than  one 
person,  in  2  instances  from  five.  In  4  instances  it  was 
found  in  the  nose  two  years,  one  year,  one  year,  and  three 
months,  respectively,  after  an  attack.  He  quotes  Arbuckle, 
medical  officer]of  health  of  Partick,  as  finding  23.1  per  cent 
of  230  contacts  infected.  In  Leith,  Fraser  and  Comrie  ^ 
found  it  in  10,  or  14  per  cent,  of  69  contacts.  Of  these  5  were 
adults  whose  children  were  sick,  and  all  of  whom  had  worked 
on  a  ship  in  the  air  of  whose  engine  room  meningococci  were 
found.  Bethge,^  immediately  after  the  appearance  of  the 
first  case  in  a  certain  institution,  found  that  of  187  persons 
66  were  carriers. 

Found  only  in  Those  near  Sick.  —  The  micrococcus  which 
is  the  cause  of  this  disease,  while  frequently  noted  in  contacts, 
is  rarely  found  in  those  not  exposed  to  the  disease.  Oster- 
mann,  when  there  were  no  cases  about,  failed  to  find  the  germ 
in  50  children  and  in  many  adults.  Bolduan  did  not  find  it 
in  150.  Kolle  and  Wassermann^  recovered  the  germs  from 
2  of  114  persons,  but  one  had  been  in  contact  with  the  disease, 
and  the  other  shortly  became  sick.  Bochalli  found  none  in 
40  men  in  a  non-infected  regiment,  Lingelsheim*  none  in 
129  persons  otherwise  sick,  and  none  in  184  non-exposed  chil- 
dren, and  he  cites  Droba  and  Kucera  as  finding  none  among 
210  children  living  where  there  was  no  meningitis.  In  23  per- 
sons not  exposed  to  the  disease  and  examined  by  Fraser  and 
Comrie  none  of  these  organisms  were  found.  Arkwright* 
failed  to  find  them  in  54  well  persons,  and  Flexner''  could 
find  none  in  50  persons  in  Philadelphia  at  a  time  when  the 
disease  was  not  present  in  the  city. 

'  Fraser  and  Comrie,  Scot.  M.  &  S.  J.,  Edinb.,  1907,  XXI,  18. 

2  Bethgc,  Dout.sche  med.  Wchnschr.,  1910,  XXXV,  66. 

'  Kolle  and  Wa'^sermann,  Klin.  Jahrb.,  Jena.,  1906,  XV,  507. 

*  LinKelshoim,  Klin.  Jahrb.,  Jena,  1906,  XV,  373. 
'  ArkwriKlit,  J.  Hyg.,  Cambridge,  1907,  VII,  145. 

•  Flexner,  J.  Exper.  M.,  N.  Y.,  1907,  IX,  105. 


50  THE  SOURCES  AND  MODES  OF  INFECTION 

As  Lingelsheim  says,  it  appears  that  the  nearer  we  approach 
cases  of  the  disease  the  more  numerous  carriers  are,  and  the 
more  extensive  the  outbreak  the  more  numerous  they  are. 
Adults  are  more  commonly  infected  than  children.  Fliigge 
thinks  that  carriers  are  ten  to  twenty  times  as  numerous  as 
cases,  and  that  is  doubtless  true. 

Infection  by  Carriers.  That  carriers  are  the  chief  source 
of  the  disease  is  the  opinion  of  those  Germans  who  have  lately 
had  experience  in  severe  outbreaks,  and  it  is  shared  by  the 
Scotch  health  officers.  Lingelsheim  says  that  there  is  no 
bacteriological  or  epidemiological  evidence  to  show  that  the 
sick  are  more  dangerous  than  the  well,  otherwise  the  cases 
would  occur  in  groups.  On  the  contrary  the  carriers  mingling 
freely  with  the  public  are  the  most  dangerous.  Jehle  ^  states 
that  23  cases  occurred  in  children  in  the  families  of  miners. 
None  of  the  miners  were  sick,  but  when  they  were  transferred 
to  another  mine,  children  there  soon  began  to  develop  the 
disease.  Their  parents  were  doubtless  carriers.  Meyer  ^ 
reports  an  instance  where  carriers  gave  rise  to  three  cases. 
At  Leith,  Buchanan^  says  that  the  first  few  cases  could  be 
traced  to  carriers,  and  Thomson^  makes  a  similar  statement 
regarding  the  early  cases  in  Lanarkshire.  Flatten^  gives  the 
details  of  numerous  instances  of  the  transmission  of  the  dis- 
ease by  well  persons. 

Carriers  explain  Spread  of  Disease.  —  Previous  to  the  dis- 
covery of  the  presence  of  the  specific  organism  of  cerebro- 
spinal meningitis  in  the  nose,  and  particularly  in  the  nose  of 
contacts,  the  mode  of  extension  of  the  disease  was  a  mystery. 
Though  certainly  an  infectious  disease,  and  appearing  in  epi- 
demics, often  quite  severe,  it  was  apparently  only  slightly  if 

1  Jehle,  cited  by  Warrington,  J.  Roy.  San.  Inst.,  Lond.,  1907,  XV,  656. 
^  Meyer,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.   Orig.,  Jena,   1909, 
XLIX,  305. 

3  Buchanan,  Brit.  M.  J.,  Lond.,  1907,  II,  852. 

«  Thomson,  Med.  Press  &  Circ,  Lond.,  1908,  n.  s.,  LXXXVI,  344. 

'  Flatten,  Khn.  Jahrb.,  Jena,  1906,  XV,  265. 


CARRIERS  AND  MISSED  CASES 


51 


at  all  contagious.  Personally,  out  of  over  a  hundred  cases,  I 
have  only  twice  seen  two  cases  in  the  same  family,  and  have, 
except  in  those  instances,  never  been  able  to  trace  connection 
between  any  two  cases.  Cases  are  frequently  treated  in  con- 
siderable numbers  in  general  hospitals  all  over  the  world,  and 
infection  of  others  has  rarely,  if  ever,  taken  place.  In  New 
York  a  greater  degree  of  contagiousness  has  been  noted  than 
in  most  places.^  Of  1500  consecutive  cases,  112,  or  7  per  cent, 
were  secondary  cases  in  the  family.  It  is  said  that  when  more 
than  one  case  occurs  in  a  family  they  all  are  usually  taken  sick 
at  about  the  same  time,^  but  this  was  not  so  in  New  York. 
The  following  shows  the  date  at  which  the  secondary  cases 
appeared  in  that  city: 


Where  First  Cases  were  removed  to 
Hospital. 

Where  First  Case  remained  at  Home 

No.  of  Secondary 
Cases. 

Interval. 

No.  of  Secondary 
Cases. 

Interval. 

14 
5 
4 

1-7  days 
1-2  weeks 
2-3      " 

3 

1  day 

2  days 

3  " 

3 

3-4      " 

5     " 

2 

4-5      " 

6     " 

3 

5-6      " 

7     " 

2 

7-8      " 

9     " 

1 

3  mos. 

11     " 

34 

18 

21     " 
30     " 

The  34  cases  which  developed  after  the  removal  of 
the  primary  case  to  the  hospital  indicate  either  that  the 
germ  of  the  disca.sc  remained  in  the  house,  on  fomites,  which 
is  highly  improbable,  as  its  powers  of  resistance  are  extremely 


»  Am.  Pub.  Health  Ass.  Rep.,  1905,  XXXI,  359. 

»  Bolduan  and  Goodwin,  Med.  News,  N.  Y,  1905,  LXXXVII,  1222. 


52 


THE  SOURCES  AND  MODES  OF  INFECTION 


slight,  or  that  unrecognized  carriers,  persons  with  the  coccus 
growing  in  the  nose,  remained  behind,  a  supposition  which 
is  entirely  in  accord  with  bacteriological  findings.  In  Glas- 
gow,^ of  194  cases,  7,  or  4.1  per  cent,  were  secondary  cases  in 
the  family.  Some  of  these  occurred  after  disinfection.  It  is 
not  unlikely  that  the  more  extensive  the  outbreak  the  more 
numerous  will  be  the  "  secondary  "  cases  in  the  family.  In 
Oppeln,  where  there  was  a  very  severe  outbreak.  Flatten  ^ 
found  the  number  of  secondary  cases  as  follows  in  successive 
months  of  the  outbreak: 


No.  of  P'amilies. 

No.  of  Cases. 

January 

February 

March 

71 
143 
257 
310 
349 
374 

79 
163 
296 
368 
414 
439 

April 

May 

June 

If,  as  appears,  the  meningococcus  is  frequently  found  in 
the  nose  of  sick  persons  and  of  contacts,  the  mode  of  exten- 
sion of  the  disease  becomes  apparent.  Observations  indicate 
that  a  very  considerable  number  of  persons  who  come  in  con- 
tact with  cases  of  this  disease  carry  the  organism  on  their 
mucous  membrane.  Yet  very  few  of  these  persons  ever  be- 
come sick.  It  appears  that  the  development  of  the  cerebro- 
spinal symptoms,  that  is  the  disease  as  we  know  it,  is  really 
a  rather  unusual  accident  of  a  not  uncommon  harmless  infec- 
tion of  the  nasal  passage.  We  can  therefore  understand  how 
the  disease,  though  apparently  showing  little  contagiousness, 
is  nevertheless  a  strictly  contagious  disease.  It  extends  almost 
entirely  through  the  agency  of  carriers.  Sometimes,  as  was 
previously  stated,  these  carriers  can  be  discovered,  particu- 

^  Rep.  Med.  Off.  Health,  Glasgow,  1906,  89. 
»  Flatten,  Klin.  Jahrb.,  Jena,  1906,  XV,  228. 


CARRIERS  AND  MISSED  CASES  53 

larly  early  in  an  outbreak.  The  appearance  of  cases  in  dif- 
ferent localities  in  a  community,  and  at  varying  intervals,  is 
readily  explained  by,  and  is  almost  a  proof  of,  the  existence 
of  a  considerable  number  of  undiscovered  carriers. 

Meningitis  an  Accident  of  Infection. — The  growth  of  the 
germs  in  the  nose  cannot  properly  be  considered  the  "incu- 
bation" of  the  disease.  Inoculation  experiments^  indicate 
that  the  nervous  symptoms  develop  in  a  very  few  hours  after 
the  specific  bacteria  are  injected  into  the  meninges.  There 
is  much  evidence,  as  given  above,  to  show  that  the  germs  may 
grow  on  the  surface  of  the  nasal  mucous  membrane  for  days, 
weeks  and  perhaps  months,  but  when  they  once  gain  access 
to  the  meninges  the  symptoms  of  the  disease  speedily 
develop. 

Meningitis  also  occurs  as  a  result  of  infection  by  the  pneu- 
mococcus.  The  disease  thus  caused  is  not  essentially  different 
from  the  epidemic  form.  The  number  of  well  carriers  of  the 
pneumococcus  is  enormously  greater,  and  is  much  more  con- 
stant than  is  the  number  of  carriers  of  the  meningococcus, 
and  the  chance  of  the  former  invading  the  meninges  and  caus- 
ing sickness  is  small,  very  much  less  than  the  chance  of  the 
latter  doing  so.  In  either  case  it  may  be  considered  an  unfor- 
tunate accident  of  a  usually  benign  infection. 

Inutility  of  Isolation  of  Meningitis.  —  If  these  views  are 
correct,  little  (-an  be  done  by  means  of  isolation  to  prevent 
the  spread  of  the  disease.  When  an  outbreak  occurs,  there 
is  certain  to  be  a  large  number  of  carriers  that  cannot  be 
found  or  isolated.  To  isolate  the  sick,  and  even  those  in 
immediate  contact  with  the  sick,  will  probably  never  make 
any  appreciable  difference  in  the  progress  of  the  disease,  that 
is  if  the  findings  of  to-day  are  confirmed  by  more  extended 
observations.  By  the  time  several  cases  have  developed  in 
a  community,  there  will  probably  usually  be  a  considerable 
number  of  carriers  who  cannot  be  found.     Stringent  isola- 

'  Lingelsheim,  Deutsche  med.  Wchnschr.,  1905,  XXXI,  1017,  1217; 
Flexner,  J.  E.xper.  M.,  N.  Y.,  1907,  IX,  142. 


54  THE  SOURCES  AND  MODES  OF  INFECTION 

tion  of  the  families  of  known  cases  will  accomplish  little,  and 
will  work  much  hardship  and  injustice. 

Diphtheria  Bacilli  in  Well  Persons.  —  Loeffler  ^  himself  in 
1884  found  diphtheria  bacilli  in  a  person  who  was  not  sick, 
and  in  1889  Roux  and  Yersin^  called  attention  to  the  per- 
sistence of  diphtheria  bacilli  on  the  mucous  membranes  of 
convalescents,  and  their  observations  were  at  intervals  sub- 
stantiated by  others.  In  1894  Park  and  Beebe  ^  examined  the 
throats  of  330  healthy  persons  who  had  not,  so  far  as  known, 
been  in  contact  with  diphtheria  cases,  and  found  diphtheria 
bacilh  in  24,  or  7.3  per  cent,  but  of  these  only  8,  or  2.4  per  cent, 
of  the  330  were  virulent.  These  authors  minimized  the  dan- 
ger to  be  apprehended  from  these  carriers,  and  although  for 
some  time  similar  observations  were  reported,  they  were  gen- 
erally, and  are  even  now  by  many,  considered  of  little  impor- 
tance. It  seems  to  me  otherwise,  and  therefore  a  considerable 
number  of  these  observations  are  here  summarized.  Miiller  * 
examined  in  routine  92  children  sick  with  diseases  other  than 
diphtheria,  in  Heubner's  clinic,  and  reported  that  12,  or  13 
per  cent,  were  infected  with  diphtheria,  but  only  6  of  the  12 
were  tested  on  guinea  pigs.  Later  18  children  in  the  same 
institution,  who  had  negative  cultures  on  admission,  were 
found  to  harbor  the  bacilli.  Kober  "^  in  Breslau  found  that 
of  600  school  children  2.5  per  cent  were  carriers  of  diphtheria 
bacilli,  but  in  only  0.83  per  cent  of  the  600  were  they  virulent. 
At  Baltimore,''  in  1899,  during  an  exceptional  prevalence  of 
diphtheria  in  a  number  of  schools,  cultures  were  taken  from 
4068  pupils'apparently  well,  and  of  these  157,  or  3.8  per  cent, 

1  Loeffler,  The  Bacteriology  of  Diphtheria,  Nuttall  and  Graham- 
Smith,  Cambridge,  1908,  31. 

'  Roux  and  Yersin,  Ann.  de  I'lnst.  Pasteur,  1890,  IV,  385. 

^  Park  and  Beebe,  Med.  Rec,  N.  Y.,  1894,  XLVI,  385;  Sci.  Bull.  1, 
Dept.  Health  N.  Y.  City,  1895. 

*  Miiller,  Jahrb.  f.  Kinderh.,  1896,  XLIII,  54. 

^  Kober,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXXI, 
433. 

0  Baltimore,  Rep.  Com.  of  Health,  1899,  96;  1900,  85. 


CARRIERS  AND  MISSED  CASES  55 

showed  diphtheria  bacilH.    The  next  year,  of  351  examined, 
23,  or  6.6  per  cent,  were  positive. 

Varieties  of  Bacilli  found.  —  Reports  of  the  finding  of  diph- 
theria bacilU  in  well  persons  would  have  more  value  if  it  were 
made  clear  what  was  meant  by  the  term  diphtheria  bacilli. 
The  bacillus  varies  greatly  in  form,  and  those  who  have 
studied  it  most  carefully  are  by  no  means  agreed  as  to  what 
should  or  should  not  be  properly  so  called.  Fortunately 
Wesbrook's  classification  of  all  these  varieties,  both  admitted 
and  questioned,  renders  it  possible  to  interpret  properly  the 
reports  of  all  who  will  take  the  trouble  to  use  his  nomencla- 
ture, and  it  is  to  be  regretted  that  more  do  not  use  it.  Again, 
diphtheria  bacilli  are  quite  as  frequently  found  in  the  nose  as 
in  the  throat,  but  few  observers  state  whether  the  cultures 
were  taken  from  throat  or  nose  or  both.  For  the  purpose  of 
securing  definite  data  from  a  large  number  of  cases,  a  col- 
lective investigation  was  undertaken  by  the  Massachusetts 
Association  of  Boards  of  Health.^  The  number  of  persons 
examined  was  4250  in  different  parts  of  the  United  States. 
Most  of  them  had  probably  not  been  directly  exposed  to  diph- 
theria except  in  Minnesota,  where  most  of  the  cultures  were 
taken  from  schools  and  institutions  where  there  had  recently 
been  cases  of  the  disease.  The  majority  of  the  persons  ex- 
amined were  adults,  and  cultures  were  taken  from  both  throat 
and  nose.  Of  all  persons  examined,  2.89  per  cent  had  "granu- 
lar "  forms  of  diphtheria  bacilli,  i.e.,  those  showing  polar 
staining  with  methylene  blue.  If  "  barred  "  and  other  aber- 
rant types  are  to  be  considered  as  diphtheria  bacilli,  as  they 
are  by  some,  the  number  of  cultures  to  be  reported  positive 
would  have  been  more  than  doubled.  Referring  only  to  the 
typical  granular  types,  1.46  per  cent  of  all  persons  showed 
throat  infection  (either  with  or  without  concurrent  nose  infec- 
tion) and  2.07  per  cent  showed  nose  infection  (either  with  or 
without  concurrent  throat  infection).  In  the  different  cities 
the  percentage  of  infected  persons  varied  from  0.43  in  Provi- 

1  J.  Mass.  .\ss.  Bda.  Health,  Bost.,  1902,  XII,  74. 


56  THE  SOURCES  AND   MODES  OF  INFECTION 

dence,  where  particular  care  was  taken  to  avoid  contacts, 
most  of  the  cultures  being  taken  from  schools  where  there 
had  been  no  diphtheria  for  at  least  two  years,  to  3.66  in  the 
Willard  State  Hospital,  and  6.03  in  Minnesota,  in  both  of 
which  localities  there  had  recently  been  diphtheria  in  the 
institutions  examined.  There  were  47  tests  for  virulence,  of 
which  8,  or  17  per  cent,  were  positive.  Recently  cultures  were 
taken  from  school  children  in  Brighton  (Boston)  by  Slack.^ 
Of  over  4000  children  examined  by  throat  and  nose  culture  on 
two  occasions,  1.93  per  cent  showed  diphtheria  bacilli.  Of 
these  8  were  tested  for  virulence,  of  which  all  proved  to  be  non- 
virulent.  Most  of  these  children  were  excluded  from  school 
until  free  from  bacilli,  but  all  of  them  had,  of  course,  been 
carrying  bacilli  in  school  for  a  longer  or  shorter  period.  No 
case  of  clinical  diphtheria  was  traced  to  any  of  these  carriers, 
either  in  school  or  out  of  school.  These  facts  have  been  ad- 
vanced as  evidence  that  the  danger  from  such  carriers  is  a 
negligible  factor  in  contrast  with  the  danger  from  conva- 
lescents whose  bacilli  are  usually  virulent.  But  in  Providence 
in  1908,  73  convalescents  carrying  diphtheria  bacilli  were 
admitted  to  school,  and  it  is  not  known  that  they  were  in  any 
instance  the  source  of  new  cases  in  the  school,  and  in  all  but 
two  or  three  instances  it  is  certain  that  they  were  not. 
Forbes  ^  cites  Meikle  as  reporting  27  carriers  discharged  from 
the  hospital  without  any  return  case.  These  facts  merely  in- 
dicate that  the  amount  of  danger  from  a  single  focus  of 
infection  is  much  less  than  is  generally  believed. 

Value  of  Bacteriological  Findings.  —  Neumann^  could  not 
find  any  diphtheria  bacilli  in  111  perfectly  normal  throats 
and  noses,  but  did  find  them  in  8  of  95  cases  suffering  from 
catarrhal  inflammation  of  the  mucous  surfaces.  He  does  not 
think  that  they  are  found  in  normal  throats,  but  certainly 
all  who  have  had  any  experience  in  taking  cultures  have  seen 

1  Slack,  Arms,  Wade  and  Blanchard,  J.  Am.  M.  Ass.,  1910,  LIV,  951. 

2  Forbes,  Brit.  M.  J.,  1909,  II,  522. 

'  Neumann,  Ztschr.f.Hyg.u.  Infectionskrankh.,  Leipz.,  1902,  XL,  33. 


CARRIERS  AND  MISSED  CASES  57 

numberless  cases  where  diphtheria  bacilH  were  found  in 
throats  which,  so  far  as  appearances  go,  were  perfectly  nor- 
mal. When  diphtheria  bacilli  are  found  on  a  reddened  or 
slightly  inflamed  mucous  surface,  the  abnormal  condition 
may  not  in  every  individual  case  be  due  to  their  presence,  for 
certainly  "  catarrhal  "  inflammations  of  nose  and  throat,  due 
to  other  causes  than  the  presence  of  diphtheria  bacilli,  are 
extremely  common.  The  evidence  is  that  at  present,  in  cities, 
from  1  to  2  per  cent  of  the  population  are  infected  with 
diphtheria  Imcilli.  The  presence  of  diphtheria  bacilli  in  an 
inflamed  throat  may  be,  then,  in  1  or  2  per  cent  of  the  find- 
ings merely  a  coincidence.  It  is  safe  to  assume  that  in  all 
but  1  or  2  per  cent  the  presence  of  diphtheria  bacilli  stands 
in  causative  relation  to  the  inflammation  of  the  surface  on 
which  they  are  found. 

Diphtheria  Bacilli  in  ChUdren.  —  In  Bristol,  Heaven'  ex- 
amined 704  children  (throat  and  nose)  connected  with  schools 
where  there  had  been  considerable  diphtheria,  and  found 
diphtheria  bacilli  in  24,  or  3.4  per  cent.  Of  758  cultures  taken 
from  schools  in  London  where  there  had  been  occasional  cases 
of  diphtheria,  58,  or  7.6  per  cent,  showed  the  bacilli."  Pen- 
nington^ examined  375  well  children  in  Philadelphia  schools, 
in  some  of  which  there  had  been  more  or  less  diphtheria,  and 
of  37  positive  cultures  from  these,  24  were  more  or  less  viru- 
lent. Of  125  pupils  from  four  other  schools  10.4  per  cent  gave 
positive  cultures,  about  half  of  which  were  virulent.  But 
Pennington  found  that  of  25  cultures  from  convalescents  22 
were  virulent.  In  the  city  of  Mexico,  of  300  school  children 
10,  or  3.3  per  cent,  showed  diphtheria  bacilli.^  Von  Sholly  ' 
examined  1000  tenement-house  children  in  New  York,  taking 
cultures  only  from  those  whose  throats  appeared  normal.   The 

»  Heaven,  Pub.  Health,  Loncl.,  1902-03,  XV,  .516. 

^  Rep.  Med.  OfT.  Health,  Lond.,  1904,  Appemlix  HI,  25. 

^  Penniii^fon,  J.  Infeet.  Dis.,  ChieaRO,  1907,  IV,  'My 

*  Fabela,  Kep.  .\in.  Pub.  Health  Ass.,  1900,  XXXH,  Pt.  2,  199. 

»  Von  iSholly,  J.  Infect.  Die.,  Chicago,  1907,  IV,  337. 


58  THE  SOURCES  AND  MODES  OF  INFECTION 

children  for  the  most  part  were  those  brought  to  hospitals 
and  dispensaries  for  treatment,  but  all  cases  were  excluded 
which  had  any  suggestion  of  sore  throat,  nasal  discharge, 
etc.  Of  these  1000  cases  5.6  per  cent  showed  diphtheria- 
like organisms,  of  which,  however,  only  1.8  per  cent  (of 
the  1000  cases)  proved  to  be  virulent.  In  50  of  the  cases 
nose  cultures  also  were  taken,  and  one  of  these  proved  to 
have  virulent  bacilli.  During  a  very  severe  outbreak  of  diph- 
theria in  Christiania,  Ustvedt'  examined  4277  school  children, 
and  found  diphtheria  bacilli  in  191,  or  4.5  per  cent.  Of  these, 
10  afterwards  developed  diphtheria.  Of  7  cultures  tested  for 
virulence  4  were  positive.  In  one  school  in  which  the  per- 
centage of  positive  cultures  was  9.2  during  the  outbreak,  it 
was  3.2  some  months  later.  In  a  school  in  the  country  where 
there  had  been  no  diphtheria  for  years,  no  bacilli  were  iso- 
lated from  86  pupils.  Ruediger^  found  diphtheria  bacilli  in 
3  of  51  normal  throats.  Gross  ^  took  two  throat  and  nose 
cultures  from  314  children  (without  diphtheria)  on  admission 
to  the  Children's  Hospital  in  Boston,  and  isolated  diphtheria 
bacilli  from  26,  or  7.9  per  cent.  Five  were  tested  for  viru- 
lence, 4  of  which  were  positive.  Hewlett  and  Murray* 
found  that  58,  or  15  per  cent,  of  385  children  on  admission  to 
the  Victoria  Hospital  for  Children  in  London,  were  diphtheria 
carriers,  and  that  in  children  under  two  years  of  age  the  per- 
centage was  21.  Cobbett  ^  at  Cambridge  reported  diphtheria 
bacilli  in  2.9  per  cent  of  650  well  persons,  many  of  whom  were 
contacts.    Some  had  mild  sore  throat. 

Diphtheria  Bacilli  in  Scarlet  Fever.  —  While  the  presence 
of  diphtheria  bacilli  in  scarlet  fever  cases  sheds  little  light 
on  their  prevalence  in  normal  throats,  it  is  of  much  interest 

^  Ustvedt,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1906,  LIV, 
147. 

2  Ruediger,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVII,  1173. 
»  Gross,  Univ.  M.  Mag.,  Phila.,  1896-7,  IX,  45. 
*  Hewlett  and  Murray,  Brit.  M.  J.,  Lond.,  1901,  I,  1474. 
"  Cobbett,  J.  Hyg.,  Cambridge,  1901,  I,  242. 


CARRIERS  AND  MISSED  CASES  59 

from  an  epidemiological  standpoint.  The  exudation  which 
frequently  covers  the  tonsils  in  scarlet  fever  is  often  mistaken 
clinically  for  a  sign  of  diphtheria,  and  such  cases  are,  before  the 
appearance  of  the  eruption,  often  reported  as  diphtheria,  so 
that  there  is  a  popular  impression  among  phj'sicians  that  the 
two  diseases  are  frequently  combined,  and  that  the  presence 
of  scarlet  fever  predisposes  to  diphtheria.  While  bacteriolog- 
ical examinations  tend  to  show  that  diphtheria  infection  on 
scarlet  fever  is  not  so  common  as  is  often  assumed,  and  that 
many  cases  reported  as  a  combination  of  the  two  diseases  are 
not  really  such,  yet  diphtheria  bacilli  are  frequently  found  in 
cases  of  scarlet  fever,  more  frequently  than  they  are  found 
in  the  general  public  from  whom  the  scarlet  fever  cases  come. 
In  Providence  during  the  past  four  years  cultures  have 
been  taken  from  92  scarlet  fever  cases  in  their  homes,  of 
which  6,  or  6.5  per  cent,  were  positive.  Of  245  cultures  in  the 
hospital,  20,  or  10.6  per  cent,  were  positive.  During  the  pre- 
ceding three  years  116  cultures  were  taken,  but  it  was  not 
recorded  whether  they  were  from  hospital  or  home  cases,  and 
of  these,  5,  or  4.3  per  cent,  were  positive.  The  excessive  per- 
centage of  positive  findings  in  the  hospital  was  due  to  infec- 
tion after  admission.  Both  throat  and  nose  cultures  were 
taken  in  nearly  every  case.  In  the  Western  Fever  Hospital 
of  London,'  of  1019  throat  swabs  taken  from  the  same  num- 
ber of  scarlet  fever  patients  on  admission,  7.86  per  cent  were 
positive;  at  another  hospital  5.41  per  cent  of  203  cases,  and 
at  another  6.8  per  cent  of  87  cases.  Of  the  939  cases  at  the 
Western  Hospital  which  did  not  have  diphtheria  bacilli  on 
admission,  6  later  developed  diphtheria,  ranging  from  the  ninth 
to  the  fifti(^th  (lay  after  admission,  and  28  more  acquired 
diphtheria  Ijuciili  without  being  sick.  Of  the  80  cases  that 
entered  infected,  4  developed  clinical  diphtheria  on  the 
fourth,  fifth,  seventh  and  thirty-first  days.  Soeronsen-  found 
that  of  1547  scarlet  fever  cases  cxamiiu'd  on  admission,  38,  or 

1  Cumpston,  J.  Hyg.,  Cambridge,  1907,  VII,  598. 

'  Soerensen,  Ztschr.  f.  Hyg.  u.  Infcctionskrankh.,  1898,  XXIX,  250. 


60  THE  SOURCES  AND  MODES  OF  INFECTION 

2.5  per  cent,  carried  diphtheria  bacilli.  During  a  service  of  two 
years  32  cases  of  diphtheria  occurred  in  the  scarlet  fever  wards 
among  about  1500  patients,  and  208  others  were  found  to  be 
infected  but  not  sick.  Ruediger^  found  diphtheria  in  4  of  75 
scarlet  fever  throats,  or  5.3  per  cent.  Garratt  and  Wash- 
bourn^  found  diphtheria  germs  in  8,  or  1.2  per  cent,  of  666 
scarlet  fever  cases.  In  Croydon,^  37,  or  17.3  per  cent,  of  213 
cases  of  scarlet  fever  were  shown  to  be  infected  with  diph- 
theria bacilli  on  admission  to  the  hospital.  In  Brighton,^  in 
1905,  33,  or  25.9  per  cent,  of  166  cases  of  scarlet  fever  had 
diphtheria  bacilli  present,  and  all  but  one  were  infected  on 
admission;  in  1907,  21  of  340  were  infected.  In  Bristol,^  of 
202  scarlet  fever  patients  in  the  hospital  in  1904,  75  per  cent 
had  positive  cultures  on  admission.  In  1905,  of  476  cases,  21 , 
or  4.4  per  cent,  were  positive,  besides  3  others  which  showed 
symptoms  of  the  disease.  In  Philadelphia,  of  700  scarlet 
fever  admissions,  11  per  cent  showed  diphtheria  bacilli. 

Percentage  of  Diphtheria  Carriers.  —  The  evidence  thus 
far  adduced  tends  to  show  that  diphtheria  bacilli  are  quite 
widely  distributed  in  the  urban  population  of  Europe  and 
America.  Perhaps  on  the  average  1  or  2  per  cent  harbor  the 
germs  of  this  disease  in  mouth  or  nose;  but  observations  also 
indicate  that  the  less  diphtheria  there  is  in  a  community, 
and  the  farther  removed  the  persons  examined  are  from  cases 
of  the  disease,  the  less  likely  they  are  to  be  infected.  Thus 
in  Christiania  during  an  outbreak,  9.2  per  cent  of  the  pupils 
in  a  certain  school  were  infected,  while  some  months  later 
the  ratio  was  only  3.2.  The  Massachusetts  Association  of 
Boards  of  Health  report  an  infection  of  6.03  per  cent  of  the 
school  children  recently  exposed  to  diphtheria  in  Minneapolis, 
while  in  schools  in  Providence  where  there  had  been  no  diph- 

^  Ruediger,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVII,  1173. 
^  Garratt  and  Washbourn,  Brit.  M.  .!.,  Lond.,  1899,  I,  893. 
'  Rep.  Med.  Off.  Health,  Croydon,  1904,  68. 
*  Rep.  Med.  Off.  Health,  Brighton,  1905,  42;  1907,  22. 
5  Rep.  Med.  Off.  Health,  Bristol,  1904,  100;  1905,  71. 


CARRIERS  AND   MISSED  CASES 


61 


theria  for  a  long  time  the  ratio  was  only  about  one-half  of 
1  per  cent. 

Percentage  among  Contacts.  —  There  are  numerous  obser- 
vations made  on  persons  brought  more  or  less  closely  in  con- 
tact with  the  sick,  which  show  that  under  such  conditions 

Percentage  of  Carriers  in  Diphtheria  Families,  Providence,  1897-1901. 


Ages. 

Persons  ex- 
amined. 

Number  of 
Carriers. 

Percentage 
of  Carriers. 

Under  1  year  .... 

119 

17 

14.2 

1    "       

112 

15 

13.3 

2  years 

97 

23 

23.7 

3     "    

112 

25 

22.3 

4     "    

116 

31 

26.7 

5     "    

120 

17 

14.1 

6     "    

137 

42 

30.6 

7     "    

130 

30 

23.1 

8     "    

119 

25 

21.0 

9     "    

113 

23 

20.3 

10     "    

139 

26 

18.7 

11      "    

79 

11 

13.9 

12     "     

127 

28 

22.0 

13     "    

86 

15 

17.4 

14     "     

88 

13 

14.7 

15     "    

70 

5 

7.1 

16     "    

64 

9 

14.0 

17     "    

57 

9 

15.7 

18     "    

57 

6 

10.5 

19     "    

45 

4 

8.8 

20     "    

34 

4 

11.7 

Adults 

2505 

277 

11.0 

Totals 

4526 

655 

14.4 

the  number  of  carriers  may  be  very  high.  For  several  years 
in  Providence  '  cultures  were  taken  from  all  the  wage  earners 
in  the  family  at  the  time  the  case  was  reported,  and  from  all 
the  members  of  the  family  for  release,  that  is,  to  determine 


Rep.  Supt.  Health,  Providence,  1901,  44. 


62  THE  SOURCES  AND  MODES  OF  INFECTION 

the  end  of  isolation.  Only  throat  cultures  were  taken.  Of 
4526  such  contacts  examined  14.4  per  cent  were  found  to  be 
infected.  If  nose  as  well  as  throat  cultures  had  been  taken, 
and  if  cultures  had  been  taken  from  the  whole  family  about 
midway  in  the  course  of  the  disease,  I  imagine  the  percentage 
would  have  been  several  times  greater.  The  preceding  table 
shows  the  percentage  infected  at  different  ages.  The  women 
in  the  family  were  infected  very  much  oftener  than  the  men. 
It  was  noticed  that  in  about  10  per  cent  of  the  cases  some 
well  member  of  the  family  remained  infected  after  the  patient 
was  entirely  free  from  germs.  In  Glasgow,^  of  2305  contacts 
in  infected  families  9.2  per  cent  were  carriers. 

Percentage  of  Carriers  in  Infected  Schools.  —  In  a  certain 
school  in  Minnesota,"  of  263  well  children,  129,  or  49  per  cent, 
were  infected  with  the  granular  and  barred  types  of  the  bacil- 
lus. In  Bristol  ^  during  a  school  outbreak  in  1907,  of  190 
well  children,  12.5  per  cent  were  carriers.  At  the  Willard  Hos- 
pital for  the  Insane  during  an  outbreak,  of  1423  well  persons, 
189,  or  13  per  cent,  were  carriers.  At  the  State  Hospital  in 
California,  11.6  of  1115  persons  were  infected.^  In  Provi- 
dence during  an  outbreak  of  diphtheria  in  an  infant  asylum, 
of  175  children  and  adults,  116  or  66.2  per  cent,  proved  to  be 
infected  at  one  time  or  another,  but  this  was  only  after  many 
repeated  cultures  extending  over  a  period  of  some  months. 
Many  of  them  were  persistent  carriers,  one  of  them  remaining 
infected  for  twenty-two  months.  Crowley  ^  in  a  school  out- 
break found  42  of  93  children  infected,  or  45  per  cent.  In 
Bermondsey,  London,''  the  children  in  diphtheria  families 
have  a  single  throat  culture  taken,  and  of  597  children  so 

1  Rep.  Med.  Off.  Health,  Glasgow,  1908,  71. 

2  Wesbrook,  St.  Paul  M.  J.,  St.  Paul,  Minn.,  1900,  II,  219  [p.  6  of 
reprint]. 

3  Rep.  Med.  Off.  Health,  Bristol,  1907,  51. 
^  Rep.  Calif.  St.  Bd.  Health,  1906-08,  201. 

5  Crowley,  J.  Roy.  San.  Inst.,  1904-05,  XXV,  807. 
«  Rep.  Med.  Off.  Health,  London,  1904,  31. 


CARRIERS  AND  MISSED  CASES  63 

examined  64,  or  10.8  per  cent,  were  found  to  be  infected.  Of 
115  well  children  in  an  institution  in  Minneapolis,  Corbet^ 
found  29,  or  25.2  per  cent,  infected.  In  several  instances  the 
bacilli  presented  atypical  forms,  but  many  of  these  were  viru- 
lent. In  a  school  in  the  same  city,  where  there  had  been  some 
diphtheria,  he  found  that  20,  or  14.3  per  cent,  of  140  cultures 
showed  the  presence  of  typical  bacilli."  Ustvedt,^  in  Chris- 
tiania,  found  17  per  cent  of  contacts  infected.  In  a  school  at 
Oakland,  California,*  25  per  cent  of  the  pupils  were  carriers. 
In  Glasgow,^  of  322  well  members  of  diphtheria  families  10.5 
per  cent  were  infected.  In  the  Duke  of  York's  school,  Lon- 
don, of  536  well  pupils  117,  or  20  per  cent,  showed  diphtheria 
bacilli,  and  of  these  10  later  had  diphtheria,  while  only  one 
of  the  "  free  "  boys  developed  it.  Of  13  cultures  from  the 
well  boys,  7  were  virulent,  though  mildly  so,  but  the  bacilli 
from  the  sick  also  showed  a  low  virulence.  It  is  worthy  of 
note  that  the  disease  recurred  in  this  school  for  two  or  three 
years.^  von  Sholly  ^  found  bacilli  in  20  of  202  contacts,  or 
about  10  per  cent,  and  of  these  14  were  virulent.  Buchanan* 
in  Glasgow  found  that  the  bacilli  were  virulent  in  66  per 
cent  of  21  healthy  carriers,  and  that  bacilli  recovered  from 
56  cases  of  the  disease  proved  virulent  only  in  74  per  cent. 
Aaser^  found  19  per  cent  of  contacts  in  cavalry  barracks  in- 
fected, and  20  per  cent  of  children  in  a  scarlet  fever  ward. 
Hellstrom '"  in  Stockholm,  of  780  soldiers  who  had  been  more 

'  Corbet,  Rep.  Com.  Health,  Minneapolis,  1905,  7. 

^  Rep.  Com.  Health,  Minneapolis,  190.3,  16. 

'  Ustvodt,  Ztschr.  f.  Hyg.  u.  Infection.skrankh.,Lcipz.,1906,LIV,  147. 

*  Bull.  Calif.  St.  Bd.  Health,  November,  1906. 
0  Rep.  Med.  Off.  Health,  GlasRow,  1906,  135. 

«  Arkwright,  J.  Hyg.,  Cambridge,  1908,  VIII,  48  ;  Rep.  Med.  Off. 
Health,  Lond,  1906,  36. 

'  von  Sholly,  J.  Infect.  Dis.,  Chicago,  1907,  IV,  337. 

*  Buchanan,  Brit.  M.  J.,  Lond.,  1909,  II,  519. 

'  A:i.ser,  Deutsche  med.  Wchn.schr.,  1S95,  XXI,  .357. 

'"  Hellstrom,  cited  by  Kobcr,  Ztschr.  f.  Hyg.  u.  Infectionskrankh., 
Leipz.,  1899,  XXXI,  433,  and  by  Fibiger,  Berl.  klin.  Wchnschr.,  1897, 
XXXIV,  753. 


64  THE  SOURCES  AND  MODES  OF  INFECTION 

or  less  in  contact  with  diphtheria,  found  151,  or  19.2  per  cent, 
infected.  Goadby,^  in  586  pupils  in  a  school  where  there  had 
recently  been  21  diphtheria  cases,  found  that  190,  or  34.1 
per  cent,  were  carriers,  and  he  quotes  Meade  Bolton  as  finding 
45.5  per  cent  of  214  contacts  infected.  Of  the  children  ex- 
amined by  Goadby  262  had  enlarged  tonsils  and  196  abnor- 
mal throats.  In  another  school  where  there  had  been  no 
reported  cases,  18  of  100  were  infected. 

Berry  and  Washbourn"  report  17,  or  11.9  per  cent,  of 
infected  contacts  in  a  school  of  142  girls.  Lister  ^  found  48 
per  cent  of  125  contacts  in  Shadwell  Hospital  infected. 
Twenty-four  of  them  had  nasal  discharge.  Park  and  Beebe* 
in  a  foundling  asylum  obtained  virulent  bacilli  and  one  non- 
virulent  form  from  5  of  55  contacts.  Fibiger,'^  during  a  school 
outbreak  of  diphtheria,  recovered  the  bacilli  in  22,  or  16.4  per 
cent,  of  134  children.  Denny  ^  found  11  per  cent  of  200  chil- 
dren infected,  in  a  school  where  there  had  recently  been  4  cases 
of  diphtheria,  and  Graham-Smith,^  10.4  per  cent  of  519  school 
children.  Gabritschewsky*  in  the  Russian  military  service 
found,  during  the  prevalence  of  diphtheria,  that  20  per  cent 
of  the  well  persons  examined  were  carriers,  and  in  a  school 
in  Moscow,  at  a  time  when  there  was  much  diphtheria,  21  of 
66  well  children  showed  diphtheria  bacilli. 

Atjrpical  Diphtheria.  —  The  old  notion  was,  and  I  fear  that 
very  many  physicians  and  not  a  few  health  officers  so  believe 
to-day,  that  diphtheria  is  a  well  defined  disease  with  charac- 
teristic symptoms.    They  cannot  imagine  diphtheria  without 

'  Goadby,  Lancet,  Lond.,  1900,  I,  236. 

^  Berry  and  Washboum,  Brit.  M.  J.,  Lond.,  1900,  I,  198. 

3  Lister,  Brit.  M.  J.,  Lend.,  1898,  II,  1338. 

*  Park  and  Beebe,  Med.  Rec,  N.  Y.,  1894,  XLVI,  385. 
=  Fibiger,  Berl.  klin.  Wchnschr.,  1897,  XXXIV,  753. 

«  Denny,  Bost.  M.  &  S.  J.,  1900,  515. 

^  Graham-Smith,  J.  Hyg.,  Cambridge,  1903,  III,  216. 

*  Gabritschewsky,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1901, 
XXXVI,  45. 


CARRIERS  AND   MISSED  CASES  65 

serious  illness.  There  always  have  been,  however,  some  acute 
clinicians  who  thought  otherwise.  Jacobi  in  New  York  was 
among  the  foremost.  He  recognized  that  the  disease  often 
presented  a  mild  type  and  that  diagnosis  was  impossible. 
He  said  in  1884:  i 

"The  sjTnptoms  are  often  but  few.  A  Httle  muscular  pain 
and  difficult  deglutition  are,  perhaps,  all  that  is  complained 
of.  Women  will  quietly  bear  it ;  men  will  go  about  their  busi- 
ness. .  .  .  There  is  as  much  diphtheria  out  of  bed  as  in  bed ; 
nearly  as  much  out  of  doors  as  indoors.  ]\Iany  a  mild  case 
is  walking  the  streets  for  weeks  without  caring  or  thinking 
that  some  of  his  victims  have  been  wept  over  before  he  was 
quite  well  himself.  .  .  .  Diphtheria  is  contagious.  Severe 
forms  may  beget  severe  or  mild  forms.  Mild  cases  may  beget 
mild  or  severe  cases." 

Under  Jacobi's  teaching  I  early  learned  to  look  for  such 
mild  cases,  and  I  remember  seeing  an  outbreak  in  a  children's 
home  during  the  early  eighties,  in  which  there  were  many 
very  mild  sore  throats  and  walking  cases.  ]\Iild  diphtheria 
of  this  type  does  not  usually  come  to  the  notice  of  a  physician, 
and  when  it  does  is  frequently  not  recognized.  How  fre- 
quent such  cases  are  it  is  difficult  to  determine,  but  they  must 
be  very  numerous.  In  a  general  hospital  at  Chelsea"  (Lon- 
don), where  there  had  been  considerable  trouble  from  out- 
breaks of  diphtheria,  it  was  determined  to  take  cultures  from 
all  patients  admitted  who  showed  any  symptoms  of  sore 
throat.  Of  815  persons  so  examined  65,  or  7.3  per  cent,  gave 
positive  cultures.  In  New  York  City^  the  school  inspectors 
were  directed  to  take  cultures  from  all  children  showing  slight 
redness  of  the  throat  or  hypertrophied  tonsils.  Of  11,451 
cultures  757,  or  6.7  per  cent,  were  positive.  These  children 
were  not  in  any  sense  considered  as  ill,  yet  the  percentage 

>  Quoted  by  Solis-Cohcn,  J.  .^m.  M.  A.ss.,  Chicago,  1907,  XLIX,  32. 

2  Parkes,  Pub.  Health,  Ixjnd.,  1902-0.3,  XV,  .538. 

»  Letter  from  Dr.  Cronin,  X.  Y.  Bd.  Health,  Sept.  23,  1904. 


66  THE  SOURCES  AND  MODES  OF  INFECTION 

infected  is  certainly  much  higher  than  would  be  looked  for 
among  the  general  school  population.  In  Hartford  ^  during 
the  years  1900-1903  cultures  were  taken  from  2038  mild  sore 
throats  seen  in  the  schools.  Of  these,  591 ,  or  29  per  cent,  were 
positive.  These  children  might  be  said  to  have  a  decided  sore 
throat,  though  they  were  all  well  enough  to  be  in  school. 
They  were  all  excluded  from  school.  During  the  same  period 
there  were  reported  in  Hartford  1537  cases  of  diphtheria,  so 
that  the  cases  found  in  the  manner  described  equaled  one- 
third  of  the  total  cases.  In  Indianapolis,^  at  a  time  when 
there  were  60  reported  cases  of  diphtheria  in  the  city,  a  dili- 
gent search  for,  and  taking  of  cultures  from,  sore  throats 
among  the  school  children  revealed  the  presence  of  46  other 
cases.  Everj'^  one  knows  how  extremely  common  sore  throat 
and  tonsillitis  are,  and  even  if  only  a  very  small  proportion, 
much  less  than  29  per  cent,  of  these,  are  true  diphtheria,  the 
number  in  the  aggregate  must  be  very  large.  I  think  I  am  well 
within  bounds  when  I  assume  that  for  every  recognized  case  of 
diphtheria  there  is  at  least  one  sore  throat  which  is  also  diph- 
theria though  unrecognized.  Judging  from  the  proportion  of 
mild  cases  in  institution  outbreaks,  the  proportion  of  unrec- 
ognized, mild,  but  yet  clinical  cases,  must  be  much  greater 
than  that.  Careful  medical  inspection  often  discovers  that 
these  missed  cases  have  been  the  source  of  reported  cases. 
For  example,  the  Report  on  the  Health  of  the  City  of  Man- 
chester (England),  1906,  gives  a  list  of  29  cases  caused  in  this 
way  during  that  year. 

Rhinitis  and  Otitis.  —  Diphtheria  sometimes  assumes  a 
chronic  form  with  few  symptoms.  Indeed  some,  as  Neumann, 
believe  that  long  persistence  of  diphtheria  bacilli  in  throat 
and  nose  is  always  accompanied  by  local  disturbance.  That 
such  is  often  the  case  in  the  nose,  and  that  subacute 
chronic  rhinitis  may  be  a  form  of  diphtheria,  and  may  give 
rise  to   typical  pharyngeal    cases,   is    generally  recognized. 

'  Reps.  Bd.  Health,  Hartford,  1900  to  1903. 

^  Rep.  Dept.  Pub.  Health  &  Charities,  IndianapoUs,  1908,  8. 


CARRIERS  AND  MISSED  CASES  67 

Park/  Abbott,-  Ravenel,^  Schaps/  Treitel  and  Koppel,^ 
DeStella,"  Ballin '  and  many  others  report  cases  of  chronic 
rhinitis  due  to  the  presence  of  the  diphtheria  bacillus.  The 
middle  ear  sometimes  suppurates  in  diphtheria,  as  it  does  in 
scarlet  fever,  though  less  frequently,  and  this  discharge  may 
remain  virulent  for  long  periods.^  I  happen  to  have  such  a 
case  under  observation  at  the  present  time. 

A  Real  Danger.  —  There  can  be  no  doubt,  then,  that  mild 
and  unrecognized  cases  of  diphtheria  are  very  common,  that 
convalescents  long  harbor  the  bacilli,  and  that  contacts  and 
other  carriers  are  very  numerous;  in  fine,  that  these  sources 
of  infection  far  outnumber  the  cases  of  recognized  sickness. 
But  are  these  really  sources  of  infection,  or  are  they,  as  so 
many  believe,  an  imaginary  danger  evolved  in  the  brain  of 
the  laboratory  worker  ?  It  is  well  again  to  emphasize  the 
fact  that  long  before  Klebs  and  Loeffler  identified  the  bacillus 
of  this  disease  a  few  able  clinical  observers  like  Jacobi  be- 
lieved that  evidence  pointed  clearly  to  the  great  danger  of 
these  unrecognized  sources  of  infection.  The  bacteriologists 
have  not  raised  the  bugaboo  of  carrier  infection,  they  have 
simply  explained  the  facts  which  observing  men  have  long 
recognized. 

Carriers  cause  Disease.  —  A  little  perusal  of  medical  liter- 
ature will  show  that  many  cases  are  reported  of  what  is 
apparently  the  distribution  of  diphtheria  by  carriers. 

Peck  ®  reports  an  instance  where  a  young  man  who  was 

»  Park,  Med.  Rec,  N.  Y.,  1892,  XLII,  121. 

•  Abbott,  Med.  News,  Phila.,  1893,  LXII,  .505. 

»  Ravenel,  Med.  News,  Phila.,  1895,  LXVI,  537. 

•  Schap.s,  Arch.  f.  Kinderh.,  Stuttg.,  1905,  XL,  80. 

»  Treitel  and  Koppel,  Arch.  f.  Kinderh.,  Stuttg.,  189.5-96,  XIX,  107. 

•  DeStclhi,  Areli.  internat.  de  hvryngol.  [etc.),  Par.,  1903,  XVI,  970. 
'  BalHn,  Jahrb.  f.  Kinderh.,  1903,  LVIII,  412. 

•  Newsholme,  Rep.  Med.  Off.  Health,  Brighton,  1900,  13;  Address  at 
Victoria  Univ.,  Manchester,  March  9,  1901,  21. 

•  .Peck,  Brit  M.  J..  Lond.,  1895,  I,  971. 


68  THE  SOURCES  AND   MODES  OF  INFECTION 

perfectly  well  but  was  a  carrier,  probably  gave  diphtheria  to 
another  young  man  with  whom  he  slept. 

In  1897  a  mother  whom  I  saw,  stayed  for  a  few  days  in  a 
house  on  a  neighboring  street  taking  care  of  a  diphtheria 
case.  Soon  after  her  return  home  her  son  was  taken  sick  with 
diphtheria,  and  when  cultures  were  taken  from  her  throat  she 
also  was  found  to  be  infected.^  In  1905  a  child  who  was  sent 
to  the  hospital  for  some  surgical  lesion  developed  scarlet 
fever  and  was  removed  to  the  scarlet-fever  ward.  Three  days 
after  his  return  home  another  child  in  the  family  was  taken 
sick  with  diphtheria,  and  a  few  days  later  a  culture  taken 
from  the  first  child  was  positive.^  Wesbrook^  reports:  "  Two 
always  well  children  carrying  bacilli  sent  home.  Diphtheria 
broke  out  shortly  after  their  arrival.  No  other  source  of 
infection  discovered.  One  always  well  girl  carrying  diph- 
theria bacilli  went  to  her  home.  Stepmother  and  children 
developed  diphtheria  within  a  few  days.  This  family  was 
practically  isolated  in  the  country." 

Hellstrom,*  during  a  diphtheria  outbreak  in  a  cavalry  regi- 
ment, noted  two  instances  in  which  perfectly  well  soldiers 
who  had  diphtheria  bacilli  on  their  mucous  membrane  car- 
ried the  disease  to  others.  Aaser  ^  reports  a  child  with  diph- 
theria germs  taking  the  disease  home  from  a  scarlet-fever 
ward  where  there  was  a  diphtheria  outbreak. 

In  1906  at  Birmingham "  there  was  a  milk  outbreak  of 
diphtheria  of  13  cases  due  to  infection  of  the  milk  by  the 
milk  handlers,  who  had  diphtheria  bacilli  in  their  throats,  but 
were  not  sick.  As  soon  as  they  were  isolated  the  outbreak 
ceased.    Similar  milk  outbreaks  caused  by  infected  well  per- 

1  Rep.  Supt.  Health,  Prov.,  1897,  21. 

2  Rep.  Supt.  Health,  Prov.,  1905,  32. 

^  Prelim.  Rep.  on  Diphtheria  in  Well  Persons,  J.  Mass.  Ass.  Bds. 
Health,  Bost.,  1901,  XI,  10. 

*  Hellstrom,  cited  by  Fibiger,  Berl.  klin.  Wchnschr.,  1897,  XXXIV, 
753. 

'  Aaser,  Deutsche  med.  Wchnschr.,  1895,  XXI,  357. 

"  Rep.  Med.  Off.  Health,  Birmingham,  1906,  40. 


CARRIERS  AND  MISSED  CASES  69 

sons  have  been  reported  from  Fitchburg/  Lowell,^  Brookline/ 
Montclair,  N.  J./  Oroville,  Cal.,^  Australia*'  and  other  places. 

At  the  Willard  State  Hospital  '  a  watchman,  who  lived 
with  his  son-in-law  in  the  village,  who  had  diphtheria,  was 
never  sick  but  was  a  carrier.  He  played  cards  with  two 
clerks,  and  they  all  drank  from  the  same  pitcher.  The  clerks, 
who  had  not  been  exposed  to  diphtheria,  were  a  week  later 
taken  sick  with  the  disease.  Four  other  instances  of  infection 
by  carriers  occurred  during  the  same  outbreak,  and  a  similar 
instance  some  years  before. 

In  Lagrange  Co.,  Ind.,^  in  1902,  there  were  three  outbreaks 
in  a  school,  apparently  caused  by  the  teacher,  in  whose  nose 
diphtheria  bacilli  were  found,  and  who  had  shown  no  symp- 
toms but  a  slight  cold.  In  Boston^  a  boy  who  had  recovered 
from  diphtheria,  escaped  from  isolation  and  went  to  Brock- 
ton, and  within  four  days  three  clinical  cases  developed  in  the 
house  where  he  visited.  Fischer  ^*^  reports  an  outbreak  traced 
to  a  restaurant  in  which  were  several  carriers  and  mild  sore 
throats.  Solberg^^  had  a  boy  who  caused  several  cases  of  the 
disease.  He  had  been  kept  in  the  hospital  for  several  months, 
but  was  finally  discharged  with  the  bacilli  present.  Cob- 
bett's^^  outbreak  in  Cambridge  was  due  to  a  boy  apparently 

'  Prelim.  Rep.  on  Diphtheria  in  Well  Persons,  J.  Mass.  Ass.  Bds. 
Health,  Bost.,  1901,  XI,  9. 

2  Rep.  Bd.  Health,  Lowell,  1904,  24. 

'  Prelim.  Rep.  on  Diphtheria  in  Well  Persons,  J.  Mass.  Ass.  Bds. 
Health,  Bost.,  1901,  XI,  9. 

*  Pediatrics,  N.  Y.,  1901,  XII,  366. 

*  Rep.  St.  Bd.  Health,  Cal.,  1906-08,  198. 

"  Armstrong,  AiKstral.  M.  Gaz.,  Melbourne,  1908,  XXVII,  350. 
'   Report  of  Epidemic  of  Diphtheria  at  Willard  State  Hospital  by 
Russell  and  Salmon  [Rep.  State  Com.  on  Lunacy,  XVI],  35  of  Reprint. 
"  Letter  from  Dr.  H.  N.  Hurty,  Sec.  Ind.  St.  Bd.  Health,  1907. 

*  Prelim.  Rep.  on  Diphtheria  in  Well  Persons,  J.,  Mass.  Ass.  Bds. 
Health,  Bo.st.,  1901,  XI,  9. 

'"  Fischer.  Munchen  med.  Wrhnschr.,  1906,  LIII,  250,  314. 
"  Solberg,  quoted  in  Pub.  Health,  Lond.,  1902-03,  XV,  515. 
"  Cobbett,  J.  Hyg.,  Cambridge,  1901,  I,  229. 


70  THE  SOURCES  AND  MODES  OF  INFECTION 

well,  but  who  for  some  weeks  had  had  a  slight  nasal  discharge 
in  which  diphtheria  germs  were  present.  Williams  ^  notes  a 
case  in  which  a  teacher  was  infected  with  clinical  diphtheria 
by  the  nasal  discharge  of  a  pupil  containing  atypical  bacilli.^ 
Newsholme  ^  saw  a  case  of  diphtheria  in  February,  1901, 
which  had  ear  discharge  for  a  short  time  only.  Suppuration 
recurred  April,  1904,  and  diphtheria  germs  were  present. 
Three  cases  of  the  disease  occurred  in  the  family  soon  after. 
The  ear  again  discharged  in  March,  1906,  with  bacilli  pres- 
ent, and  a  sister  apparently  contracted  the  disease  from  this 
source.  Newsholme  had  a  similar  case  in  1907.  Vance* 
states  that  a  nurse  had  diphtheria  in  June,  and  after  one 
negative  culture  from  the  throat,  went  home  and  infected  3 
persons.  In  August  she  returned  to  the  hospital  and  infected 
4  other  persons,  at  which  time  a  culture  from  throat  and  nose 
was  negative.  Subsequent  cultures  proved  positive,  and 
continued  so  until  late  in  November.  Strain  ^  also  reports  a 
nurse  in  whose  nose  diphtheria  bacilli  were  found  intermit- 
tently for  nine  months,  but  they  were  never  present  in  the 
throat.  Edsall  **  notes  five  outbreaks  due  to  carriers,  and 
Solis-Cohen'  seven  such  outbreaks.  Cameron^  reports  that 
in  70  instances  cases  of  scarlet  fever  discharged  from  the  Lon- 
don hospitals  carried  diphtheria  to  their  homes,  and  that  in 
many  of  these  carriers  diphtheria  bacilli  were  shown  to  be 
present. 

Similar  cases  in  which  clinical  diphtheria  is  apparently  con- 
tracted from  perfectly  well  convalescents  or  carriers,  or  from 
slight  unnoticed  sore  throat,  or  from  rhinitis,  are  found  scat- 

1  Williams,  J.  Laryngol.,  Lond.,  1905,  XX,  591. 

'  Wesbrook's  D'D^ 

^  Newsholme,  Rep.  Med.  Off.  Health,  Brighton,  1906,  13. 

*  Vance,  Intercolon.  M.  J.  Australas.,  Melbourne,  1908,  XIII,  152. 

*  Strain,  Lancet,  Lond.,  1908,  II,  1143. 

«  Edsall,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  125. 

'  Solis-Cohen,  J.  Arp.  M.  Ass.,  Chicago,  1909,  LII,  111. 

*  Cameron,  Rep.  to  Asylums  Bd.  on  Return  Cases  of  Scarlet  Fever 
in  London,  1901-02,  41. 


CARRIERS    AXD   MISSED   CASES  71 

tered  through  medical  literature,  and  a  number  of  such  have 
been  collected  by  the  Massachusetts  Association  of  Boards 
of  Health/  Nuttall  and  Graham-Smith/  Newsholme,^  Sit- 
tler/  Niven/  Schneider,"  mj'self  ^  and  others. 

Chronic  Diphtheria.  —  Diphtheria  sometimes  assumes  a 
chronic  form,  with  few  constitutional  sj'mptoms,  and  little 
that  is  noticeable,  and  nothing  that  is  characteristic  in  the 
fauces.  This  condition  may  continue  for  months,  and  is 
sometimes  accompanied  by  considerable  antitoxin  in  the 
blood.    Such  cases  may  cause  typical  diphtheria.^ 

Glanders.  —  According  to  veterinary  writers  ^  the  infec- 
tion of  glanders  often  remains  latent,  and  also  many  mild 
chronic  cases  occur  which  are  the  source  of  considerable  out- 
breaks. The  Bureau  of  Animal  Industry  ^^  reports  an  instance 
where  a  horse  was  apparently  infectious  for  eight  years  with- 
out manifesting  any  symptoms  which  would  lead  even  an 
expert  to  suspect  the  infection.  Another  instance  was  given 
of  a  year-long  infection  of  an  apparently  w^ell  animal. 

Influenza.  —  The  rapidity  with  which  epidemic  influenza 
spreads,  its  sudden  contemporaneous  appearance  at  many 
distant  points,  and  the  difficulty  of  tracing  the  route  of  infec- 
tion, render  it  almost  certain  that  there  must  in  this  disease 
be  many  mild  atypical  cases,  and  many  persons  infected,  but 
showing  no  symptoms.    That  the  disease  is  not  carried  by 

*  Prelim.  Rep.  on  Diphtheria  Bacilli  in  Well  Persons,  J.  Mass.  Ass. 
Btls.  Health,  Bost.,  1901,  XI,  9. 

2  Nuttall  and  Graham-Smith,  The  Bacteriology  of  Diphtheria,  Cam- 
bridge, 1908,  311. 

'  Newsholme,  Address  at  Victoria  Univ.,  Manchester,  Mar.  9,  1904, 
and  Med.-Chir.  Tr.,  Lond.,  1904,  LXXXVII,  W9. 

*  Sittlcr,  Milnchen  mod.  Wchn.schr,  1906,  LIII,  863. 

*  Niven,  Rep.  on  the  Health  of  Manchester,  1908,  204. 

*  Schneider,  Ztschr.  f.  Med.-Beamte,  Berl.,  XX,  698. 

'  Rep.  Supt.  Health,  Prov.,  1897,  19;  1898,  23;  1905,  32. 
'  Neissor  and   Kahnert,   Deutsche  med.  Wchnschr.,    1900,   XXVI, 
525,  and  Nci.s.«or,  Dcut.scho  med.  Wchnschr.,  1902,  XXVHI,  719. 
"  Law,  Te.\t-B()()k  of  Veterinary  Medicine,  Ithaca,  1902,  IV,  235. 
'"  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Circ.  x\o.  78,  4. 


72  THE  SOURCES  AND  MODES  OF  INFECTION 

the  air  over  long  distances,  as  has  been  urged  by  many,  but 
is  invariably  transmitted  by  persons,  has  been  shown  by  Par- 
sons, Schmid  and  others.  That  these  persons  often  show  no 
symptoms,  and  are  not  suspected  of  being  carriers,  also  seems 
certain. 

There  is  some  bacteriological  evidence  of  this,  but  the  bac- 
teriologists have  not  given  to  the  study  of  this  disease  the 
attention  which  it  deserves.  Finkler  found  the  bacillus  in 
the  sputum  a  year  after  the  beginning  of  an  attack.  Lord,^ 
during  non-epidemic  periods,  in  examining  cases  of  what 
appeared  ordinary  cough,  found  influenza  bacilli  present  in 
60  per  cent  of  the  cases.  Later, ^  in  18G  non-tuberculous  cases, 
mostly  bronchitis,  he  found  the  bacillus  frequently  present, 
often  in  almost  pure  culture.  Boggs^  has  also  found  chronic 
cases  somewhat  simulating  tuberculosis,  in  one  instance  last- 
ing for  a  year.  Holt,*  in  the  Babies'  Hospital  in  New  York, 
obtained  112  positive  cultures  out  of  312  taken  from  198 
persons.  Of  48  healthy  persons  16  yielded  positive  cultures. 
I  have  found  scarcely  any  other  reports  of  the  examination 
of  well  persons  for  this  organism,  but  the  frequency  with 
which  it  is  found  in  those  sick  with  other  diseases  is  evidence 
of  the  widespread  distribution  of  the  bacillus.  Wollstein,^  by 
swabbing  the  throat,  found  the  bacillus  in  16  of  37  cases 
of  pneumonia,  in  11  of  34  of  bronchitis,  in  8  of  18  cases  of 
measles,  in  8  of  16  of  tuberculosis,  but  only  5  times  in  65  cases 
of  other  diseases.  Davis  ^  found  influenza-like  bacilli  in  normal 
throats,  and  in  61  of  68  cases  of  whooping  cough  and  in  13 
of  23  cases  of  measles.  Inoculated  on  the  mucous  surface  of 
a  healthy  young  man,  fever  and  catarrhal  symptoms  devel- 
oped.    Both  Davis  and  Wollstein  consider  that  the  so-called 

1  Lord,  Boston  M.  &  S.  J.,  1902,  CXLVII,  662. 

2  Lord,  Boston  M.  &  S.  J.,  1905,  CLII,  574. 

3  Boggs,  Am.  J.  M.  Sc,  Phila.,  1905,  n.  s.,  CXXX,  902. 
*  Holt,  Am.  J.  Obst.,  N.  Y.,  1909,  LX,  343. 

6  Wollstein,  J.  Exper.  M.,  N.  Y.,  1906,  VIII,  681. 

"  Davis,  J.  Am.  M.  Ass.,  Chicago,  1907,  LXVIII,  1563. 


CARRIERS  AND   MISSED  CASES  73 

pseudo-influenza  bacilli  in  their  different  forms  are  of  the 
same  "  species  "  as  the  typical  forms.  Others  have  found 
the  bacillus  in  other  infectious  diseases,  as  Leibscher  ^  and 
Auerbach,'  the  latter  of  whom  obtained  it  in  5.4  per  cent  of 
700  cases  of  diphtheria,  scarlet  fever,  etc. 

The  Coccus  of  Pneumonia.  —  That  the  pneumococcus  is 
present  in  the  saliva  of  normal  mouths  was  early  recognized 
by  Pasteur,  Sternberg,  Welch  and  others,  and  is,  of  course,  a 
now  well-established  fact.  Recently  a  number  of  careful 
observations  have  been  made  to  determine  the  frequency  of 
its  occurrence,  its  virulence,  and  variations  in  form  and  habits 
of  growth.  Buerger^  found  it  present  in  50  per  cent  of  78 
normal  mouths,  and  in  34.8  per  cent  of  204  normal  throats 
not  so  carefully  examined.  He  also  found  that  it  could  be 
recovered  for  weeks  from  convalescents.  Of  the  cultures  from 
normal  mouths  79  per  cent  proved  virulent.  Hiss*  found  it 
in  14  of  22  persons,  and  Duval  and  Lewis  ^  in  all  of  24  per- 
sons about  the  laboratory.  Longcope  and  Fox"  obtained  it  in 
40  per  cent  to  50  per  cent  of  mouths  examined.  It  was  more 
often  found  and  more  virulent  in  winter.  Frost,  Divine  and 
Reineking  ^  found  it  in  36  per  cent  of  healthy  mouths,  23  per 
cent  in  autumn,  43  per  cent  in  winter  and  50  per  cent  in  the 
spring.  The  organism  may  persist  in  the  same  individual 
for  months.  Park  and  Williams  ^  report  the  pneumococcus 
as  prevalent  both  in  city  and  country,  as  do  others,  but  note 
that  germs  from  normal  mouths  are  less  virulent  for  rabbits 

'  Leibscher,  Prag.  med.  Wchnschr.,  1903,  XXVIII,  85. 
'  Auerbach,    Ztschr.    f.    Hyg.    u.    Infcctionskrankh.,    Leipz.,    1904, 
XLVII,  259. 

•  Buerger,  J.  Expcr.  M.,  N.  Y.,  1905,  VII,  497. 

•  Hiss,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  547. 

'  Duvul  and  Lewis,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  473. 

•  Longcope  and  Fox,  J.  Expcr.  M.,  N.  Y.,  1905,  VII,  430. 

'  Frost,  Divine  and  Reineking,  J.  Infect.  Dis.,  Chicago,  1905  [Suppl. 
No.  1],  298. 

'  Turk  and  Williams,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  403. 


74  THE  SOURCES  AND  MODES  OF  INFECTION 

than  those  from  cases  of  pneumonia.  Wells  ^  fomid  pneu- 
mococci  in  the  throat  or  upper  respiratory  passages  in  45  per 
cent  of  135  persons,  and  Besser  ^  found  them  in  14  per  cent 
of  the  noses  of  57  well  persons,  and  Hasslauer  ^  in  24  of  111 
normal  noses.  Ruediger  *  got  positive  results  in  90  per  cent 
of  51  normal  throats,  in  91.4  per  cent  of  71  scarlet  fever 
throats,  in  12  of  14  cases  of  measles,  and  in  8  of  9  cases  of 
tonsillitis,  or  pharyngitis. 

Gonorrhea.  —  That  gonorrhea  assumes  a  latent  form  in 
both  men  and  women,  showing  no  signs  whatever  for  con- 
siderable periods,  and  relapsing  into  a  subacute  or  even  acute 
condition  after  it  was  supposed  to  be  cured,  has  long  been 
known.  But  it  is  only  since  the  discovery  of  the  gonococcus 
that  the  latency  of  this  infection,  as  well  as  its  persistence, 
has  been  fully  appreciated,  just  as  it  has  only  been  the  rec- 
ognition of  this  coccus  which  has  shown  the  serious  patho- 
logical changes  in  important  organs  which  often  follow 
gonorrhea.  There  has  also  been  demonstrated  recently  the 
frequent  innocent  transmission  of  the  disease  among  young 
children.  All  the  text-books  and  monographs  dealing  with 
gonorrhea  dwell  on  these  facts,  and  refer  to  the  finding  of 
the  germ  in  cases  long  supposed  to  be  well,  and  to  its  per- 
sistence for  long  periods  of  time."  A  physician  told  me  of  a 
case  lasting  from  the  third  year  of  life  to  the  twenty-eighth. 
Some  striking  instances  of  the  latency  of  gonorrhea  are  given 
by  Chapman,*^  and  he  has  shown  me  records  of  many  more 
in  which  unsuspected  infection  had  lasted  for  many  years. 
The  same  author  states  that  the  gonococcus  may  be  encysted 

1  Wells,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  361. 

^  Besser,  Beitr.  z.  path.  Anat.  u.  z.  allg.  Path.,  Jena,  1889,  VI,  331. 

^  Hasslauer,  Centralbl.  f.  Bakteriol.  [etc.],  Ist  Abt.  Ref.,  Jena,  1905, 
XXXVII,  1. 

*  Ruediger,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVII,  1171 

«  Wertheim,  Arch.  f.  d.  Geburtsh.,  Jena,  1902,  XLII,  192. 

»  Chapman,  Fiske  Fund  Prize  Essay,  Providence,  1905,  The  SequelsD 
of  Gonorrhea,  etc.,  31. 


CARRIERS  AND  MISSED  CASES       '  75 

or  dormant  in  tubal  or  ovarian  tissue  indefinitely.  Rathbun 
and  Dexter  '  from  a  clinical  and  careful  bacteriological  study 
of  cases  show  that  infection  often  persists  long  after  the 
patient  is  apparently  cured,  and  that  such  uncured  cases  are 
far  more  common  than  is  generally  believed.  Hamilton  ^ 
refers  to  the  difficulty  of  demonstrating  the  coccus  in  mild 
and  chronic  cases,  and  states  that  such  cases  are  very  com- 
mon. Nottshaft  ^  followed  120  cases  of  gonorrhea  and  ob- 
tained the  gonococcus  from  73  per  cent  during  the  second 
six  months.  During  the  fourth  six  months  the  percentage 
fell  to  18,  and  in  the  third  year  the  gonococci  still  per- 
sisted in  6  per  cent  of  the  cases.  This  latency  is  the  chief 
cause  of  innocent  marital  infections.  It  is  also  one  reason 
why  the  medical  supervision  of  prostitution  can  never 
have  much  effect  in  restricting  the  disease.  No  practicable 
amount  of  inspection  would  ever  guarantee  freedom  from 
infection. 

Tubercle  Bacilli  in  Mouth  and  Nose.  —  There  are  two 
conditions  under  which  tubercle  bacilli  may  exist  in  human 
beings  without  appreciable  symptoms. 

First,  they  may  be  found  on  the  mucous  surfaces  of  mouth, 
throat,  or  nose.  Straus  ^  examined  the  nose  of  29  well  per- 
sons, orderlies,  nurses  and  physicians  about  tuberculosis 
wards,  and  recovered  tubercle  bacilli  from  9.  Cornet  found 
them  in  his  own  nose. '  Jones,®  by  inoculating  animals  with 
mucus  from  the  nose  of  31  persons  not  brought  into  par- 
ticularly close  contact  with  consumptives,  demonstrated  the 
presence  of  tubercle  bacilli  in  11.    Similar  results  have  been 

»  Rathbun  and  Dexter,  N.  York  M.  J.  [etc.],  1909,  XC,  241. 

*  Hamilton,  J.  Infect.  Dis.,  Chicago,  1908,  V,  134. 

'  Nottshaft,  Die  Chronische  Gonorrhea  der  Mansliche  Harnrohre, 
Leipzig,  1905. 

*  Straus,  Arch,  de  med.  exper.  et  d'anat.  path.,  Par.,  1894,  VI,  633. 

*  Cornet,  Nothnagels  Encyclopedia,  Phila.  and  Lond.,  1907,  Tuber- 
culosis, 152. 

«  Jones,  Med.  Rec,  N.  Y.,  1900,  LVIII,  285. 


76  THE  SOURCES  AND  MODES  OF  INFECTION 

reported  by  Mbller  ^  and  Bernheim.-  Persons  in  the  vicinity 
of  consumptives  must,  unless  great  care  be  taken,  receive  a 
certain  number  of  tubercle  bacilli  upon  their  mucous  sur- 
faces. Whether  they  increase  in  numbers  in  such  a  location 
is  not  shown  by  the  observers  quoted,  but  unless  they  do  it 
seems  rather  surprising  that  they  can  be  demonstrated  in 
such  a  proportion  of  cases.  On  the  other  hand,  it  does  not 
seem  likely  that  conditions  in  the  mouth  and  nose  are  favor- 
able for  the  growth  of  this  bacillus,  and  the  weight  of  evi- 
dence seems  to  be  that  the  tubercle  bacillus  does  not,  to  any 
extent  at  least,  develop  on  the  normal  mucous  membrane 
of  the  throat  or  nose  of  well  persons. 

Blair  ^  reports  finding  tubercle  bacilli  in  the  nose  of  various 
wild  animals  in  captivity. 

Latent  Tuberculosis.  —  That  the  tubercle  bacilli  invade 
the  tissues  ^nd,  creating  little  disturbance,  remain  latent  for 
a  considerable  period  of  time,  has  been  amply  demonstrated. 
While  there  are  not  many  who  believe  that  this  latency  is 
so  universal  or  so  persistent  as  does  von  Behring,  yet  it  is 
certainly  not  a  rare  phenomenon,  h.  Rabinowitsch^  in  a 
recent  article  gives  a  short  resume  of  the  work  of  various 
observers,  and  Harbitz  ^  has  also  discussed  it  in  an  article 
on  tuberculosis  of  children.  Harbitz,  in  142  autopsies  of  chil- 
dren who  were  clinically  free  from  tuberculosis,  and  in  whose 
glands  no  macroscopic  or  microscopic  signs  of  the  disease 
could  be  seen,  nevertheless  was  able  by  inoculation  to  dem- 
onstrate the  presence  of  virulent  tubercle  bacilli.  Rabino- 
witsch  reports  four  cases  of  virulent  bacilli  in  lymph  glands 
that  had  undergone  calcareous  degeneration,  thus  indicating 
a  long-standing  latency.    Many  similar  observations  by  other 

'  Mbller,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXXII, 
205. 

'  Bernheim,  Clinique,  Brux.,  1905,  XIX,  346. 
'  Blair,  J.  Comp.  M.  &  Vet.  Arch.,  1903,  XXIV,  278. 
'  Rabinowitsch,  Berl.  klin.  Wchnschr.,  1907,  XLIV,  35. 
6  Harbitz,  J.  Infect.  Dis.,  Chicago,  1905,  II,  143. 


CARRIERS  AND  MISSED  CASES  77 

writers  are  given  by  those  just  quoted,  and  Gaffky  ^  has 
recently  reported  finding  the  glands  of  11  per  cent  of  246  well 
persons  as  containing  living  bacilli,  demonstrated  by  inocu- 
lation tests.  Tubercle  bacilli  are  found  in  the  tonsils  as  well 
as  in  the  Ij^mpli  glands.  Lartigau  and  Nicoll  ^  found  infected 
adenoids  in  12  of  75  healthy  children,  and  Weichselbaum  and 
Bartel,'  Goodale  *  and  Cornet  °  report  similar  findings. 

Leprosy.  —  Sticker  ^  says  that  lepra  bacilli  often  remain 
latent  in  the  nose  for  long  periods. 

Bacteria  of  Suppuration,  Latency.  —  As  has  been  stated  on 
page  20,  pus  bacteria  are  normal  inhabitants  of  the  skin  and 
mucous  surfaces,  and  may  even  invade  the  glands  and  other 
deeper  tissues  and  remain  latent  for  long  periods  of  time. 
They  may  later,  as  the  result  of  traumatism,  be  carried  by 
the  circulation  to  distant  organs,  there  causing  suppuration.^ 
Among  those  who  have  demonstrated  the  latency  of  infection 
with  pus-forming  bacteria  may  be  mentioned  Manfredi  and 
Viola,^  Kalble,^  Perez  **'  and  Hess."  Conradi ''  seems  to  have 
employed  an  improved  technique  in  his  work,  and  has  demon- 
strated bacteria  in  72  of  162  apparently  healthy  organs  taken 

*  Gaffky,  Konferenz  Internat.  f.  Tuberk.,  Wien,  1907. 

^  Lartigau  and  Nicoll,  Am.  J.  M.  Sc,  Phila.,  1902,  n.  s.,  CXXIII, 
1031. 

»  Weichselbaum  and  Bartel,  Wien  klin.  Wclinschr.,  1905,  XVIII,  241. 

*  Goodale,  Boston  M.  &  S.  J.,  1906,  CLV,  278. 

"  Cornet,  Nothnagels  Encyclopedia,  Phila.  and  Lond.,  1907,  Tuber- 
culosis, 158. 

*  Sticker,  Arb.  a.  d.  k.  Gesndhtsamtc.,  Berl.,  1899,  XVI,  Anlage  I. 
'  Soprano,  Central})!,  f.  Baktoriol.  [etc.],  l.st  Abt.  Orig.,  Jena,  1906, 

XLI,  601. 

"  Manfrodi  and  Viola,  Ztschr.  f.  Hyg.  u.  Infcctionskrankh.,  Leipz., 
1899,  XXX,  64. 

»  Kalblo,  Miinchen  med.  Wchn.schr.,  1899,  XLVI,  622. 

'"  Perez,  Jahresb.  u.  d.  Fortschr.  .  .  .  d.  path.  Mik.  Baumgarten, 
1897,  XIII,  894. 

"  Hes.s,  Centralbl.  f.  Bakteriol.  (etc.),  Ist  Abt.  Orig.,  Jena,  1907, 
XLIV,  1. 

"  Conradi,  Miinchen  med.  Wchnschr.,  1908,  LV,  1523. 


78  THE  SOURCES  AND  MODES  OF  INFECTION 

from  150  healthy  animals.  Ford^  and  Dudgeon^  also  report 
finding  bacteria,  especially  pus-forming  types,  lying  latent  in 
healthy  organs.  Bardley^  fomid  bacteria  pathogenic  for  rab- 
bits in  196  of  200  atrophied  tonsils,  and  in  101  he  demon- 
strated Streptococcus  pyogenes. 

Latent  Tetanus.  —  Canfora  *  and  Vincent  ^  have  both 
shown  that  tetanus  spores  may  be  injected  into  the  body 
and  remain  latent  for  some  time. 

Latency  a  Common  Phenomenon.  —  The  carrying  of  pus- 
forming  organisms  and  tubercle  bacilli  without  symptoms, 
and  the  latency  of  both  infections,  are  of  little  practical  im- 
portance to  the  health  officer,  for  such  latent  infections  are 
not  a  source  of  danger  to  others.  The  fact  of  the  latency  is 
touched  upon  here  to  show  how  general  is  the  phenomenon. 
The  laity  and  a  large  number  of  physicians  are  incredulous 
that  there  should  be  diphtheria  infection  unless  the  patient 
is  sick  in  bed  with  the  throat  choked  with  exudation,  or  that 
there  can  be  scarlet  fever  without  high  fever  and  extensive 
eruption.  It  is  to  show  to  such  that  latency,  and  infection 
with  slight  symptoms,  are  phenomena  belonging  not  only  to 
diphtheria,  typhoid  fever  and  scarlet  fever,  but  to  many  other 
infectious  diseases,  that  these  facts  are  here  presented. 
Infection  without  symptoms  is  no  cause  for  surprise,  but 
may  be  expected  in  any  parasitic  disease.  There  may  be 
exceptions,  as  is  said  to  be  the  case  in  relapsing  fever, 
but  these  exceptions,  rather  than  the  existence  of  latency 
and  atypical  types,  should  be  cause  for  surprise. 

Likeness  of  Scarlet  Fever  and  Diphtheria.  —  Unfortunately 
we  do  not  know  the  nature  of  scarlet  fever  virus,  hence  many 
important  matters  relating  to  the  causation  of  this  disease 

1  Ford,  J.  Hyg.,  Cambridge,  1901,  I,  277. 

2  Dudgeon,  Lancet,  Lond.,  1908,  II,  1651. 

3  Bardley,  Johns  Hopkins  Hosp.  Bull.,  Bait.,  1909,  XX,  88. 

*  Canfora,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena,  1907, 
XLX,  495. 

*  Vincent,  J.  de  physiol.  et  de  path,  gen..  Par.,  1908,  X,  664. 


CARRIERS  AND   MISSED  CASES  79 

are  in  doubt.  There  are  many  points  of  resemblance  between 
this  disease  and  diphtheria,  such  as  the  degree  of  infective- 
ness,  the  apparent  variation  in  the  period  of  incubation  and 
duration  of  infection,  the  verj^  brief  incubation  in  some  cases, 
the  persistence  of  infection  in  some  instances  long  after  recov- 
ery and  the  contrary  fact  of  the  early  loss  of  infectivity  in 
many  instances,  the  prominence  of  the  initial  throat  symp- 
toms, and  the  occurrence  of  albuminuria  and  middle  ear 
inflammations.  We  are  justified,  I  think,  in  looking  for  a  bac- 
terial infection,  and  the  probability  is  that  scarlet  fever  is 
in  the  main,  like  diphtheria,  a  local  disease  of  the  mucous 
surfaces,  chiefly  of  the  throat  and  nose.  We  certainly  see 
many  mild  atypical  cases  of  scarlet  fever  just  as  we  do  of 
diphtheria,  probably  fully  as  manj- ,  and  we  naturally  expect 
to  find  also  true  carriers  who  exhibit  no  symptoms  at  all. 

Atypical  Scarlet  Fever.  —  As  tlie  bacteriologist  cannot  help 
us,  we  have  to  rely  on  clinical  evidence,  which  is  much  more 
uncertain  and  difficult  to  secure.  The  lajTnan  and  the  inex- 
perienced physician  are  apt  to  scoff  at  the  suggestion  of  scarlet 
fever  unless  the  patient  has  a  high  fever  and  is  as  red  as  a 
lobster.  But  all  who  have  seen  much  of  this  disease  know 
that  it  is  exceedingly  common  to  see  cases  with  a  scarcely 
discernible  indefinite  rash  lasting  for  only  a  few  hours,  a  rise 
in  temperature  of  only  a  degree  or  two  lasting  also  only  a 
few  hours,  and  the  merest  trace  of  sore  throat.  Sometimes 
the  rash  may  be  entirely  absent  and  even  the  fever  may 
escape  the  most  careful  observation.'  In  institutions  and 
families,  such  ca.ses,  considered  doubtful  at  first,  or  perhaps 
entirely  neglected,  prove  to  be  the  origin  of  typical  symptoms 
in  others.  Every  health  officer  will  recall  many  such  cases. 
They  are  the  missed  cases  which  are  such  a  factor  in  the 
maintenance  of  this  disease.  There  are  many  references  to 
them  in  the  reports  of  health  oflficers  and  in  medical  litera- 
ture.   Among  others  who  re{)ort  such  atypical  cases  are  News- 

»  Caziot.BulI.  et  mom.,  Soc.  mcd.d.  hop.  de  Par.,  1903,  n.s.,  XX,  799; 
Semaine  med.,  Par.,  1903,  XXIII,  205. 


80  THE  SOURCES  AND   MODES  OF  INFECTION 

holme/  Caziot,^  Welch  and  Schamberg,^  Cameron/  Butler  ^ 
and  Thornton  and  Mader  referred  to  below.  In  most  of 
these  missed  cases  there  were  some  slight  symptoms,  though 
overlooked  or  misunderstood  at  the  time.  In  Manchester, 
in  1906,  there  were  discovered  229  missed  cases,  mostly  of  a 
mild  character.  From  these  139  other  cases  had  developed." 
Number  of  Atypical  Cases.  —  It  is  difficult  to  estimate  the 
number  of  atypical  cases  of  scarlet  fever.  Probably  it 
varies  according  to  the  extent  and  severity  of  the  outbreak, 
and  for  other  reasons.  Newsholme  ^  has  reported  a  milk  out- 
break in  which  the  number  of  sore  throats  without  the  pres- 
ence of  eruption  was  215,  while  the  number  of  typical  cases  of 
scarlet  fever  was  only  38.  Butler,^  at  Wellesden,  studied  the 
incidence  of  sore  throat  in  families  where  there  was  reported 
scarlet  fever,  and  found  that  31.2  per  cent  of  1266  persons  in 
such  families  had  sore  throat,  while  only  2.8  per  cent  of  1644 
persons  living  in  families  where  there  was  no  scarlet  fever 
had  sore  throat.  In  a  school  with  300  children  Thornton' 
found  31  typical  eases,  19  cases  with  no  rash  and  slight  sore 
throat,  and  46  cases  in  which  only  desquamation  was  noticed. 
Mader  ^"  observed  9  typical  and  12  very  atypical  cases  in  an 
outbreak  in  a  home  for  epileptics.  True  "carriers,"  that  is, 
perfectly  well  persons,  are  sometimes  reported.  Thus  I  have 
noted  an  instance  where  a  woman  apparently  in  this  way 
carried  scarlet  fever  to  her  child.   She  had  been  taking  care  of 

1  Newsholme,  Tr.  Med.-Chir.  Soc,  Glasg.,  LXXXVII,  549. 

"  Caziot,  Bull,  et  mem., Soc.  med.  d.  hop.  de  Par.,  1903,  n.s.,  XX,  799; 
Semaine  med.,  Par.,  190.3,  III,  205. 

'  Welch  and  Schamberg,  Acute  Infectious  Diseases,  Phila.,  1905,  390. 

*  Cameron,  Rep.  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria 
to  Asylums  Bd.,  Lond.,  1901-02,  38,  78. 

6  Butler,  Proc.  Roy.  Soc.  Med.,  Lond.,  1908,  I,  Epidemiol.  Sec,  225. 

^  Rep.  on  Health  of  Manchester,  1906,  43. 

'  Newsholme,  Rep.  Med.  Off.  Health,  Brighton,  1906,  48. 

'  Butler,  Rep.  Med.  Off.  Health,  Wellesden,  1907,  76. 

»  Thornton,  Brit.  M.  J.,  Lond.,  1908,  I,  495. 

'"  Mader,  Cor.-Bl.  f.  schweiz.  Aerzte,  1908,  XXXVIII,  169. 


CARRIERS  AND  MISSED  CASES  81 

another  child,  and  after  an  entire  change  of  clothing,  bath  and 
shampoo,  visited  the  first-named  child,  who  was  taken  sick  two 
days  later.  Newsholme  reports  what  he  thinks  are  possibly, 
or  even  probably,  similar  cases.  Newman,^  of  Finsbury  (Lon- 
don), noted  5  carriers  among  school  children,  three  of  whom, 
though  they  had  never  had  the  disease,  transmitted  it  to 
others.  Kerr  ^  also  reports  5  such  cases.  When  a  diphtheria 
patient  discharged  from  a  hospital  carries  scarlet  fever  home 
to  his  family,  he  must  in  most  instances  be  considered  a  true 
'  carrier,  for  it  is  unlikely  that  symptoms  of  scarlet  fever  would 
often  escape  notice  in  the  hospital.  Ten  of  this  sort  of  return 
carriers  are  reported  by  Simpson,^  30  by  Cameron'*  and  44 
by  Turner." 

Smallpox.  —  There  is  still  doubt  as  to  the  specific  cause 
of  smallpox.  The  claims  that  have  been  advanced  in  favor 
of  this  or  that  micro-organism  have  not  as  yet  been  substan- 
tiated. Hence  there  is  no  "  laborator}^  "  evidence  that  car- 
riers of  this  disease  exist,  nor  is  there  much  clinical  evidence 
that  perfectly  well  persons  transmit  the  disease.  There  are, 
it  is  true,  scattered  through  medical  literature  numerous 
reports  of  instances  of  such  transmission.  These  reports,  as 
often  in  other  diseases,  are,  as  regards  the  evidence,  rather 
unsatisfactory.  There  is  usually  a  possibility  of  such  trans- 
mission, no  actual  demonstration.  Nevertheless  it  is  quite 
possible  that  there  may  be  true  carriers  of  smallpox,  and 
there  may  be  a  considerable  number  of  them.  Mild  cases 
are  often  very  numerous.  This  was  well  illustrated  in  the 
recent  epidemic  in  the  United  States  and  England.     In  the 

'  Newman,  Rep.  Med.  Off.  Health,  Lond.,  1904,  27. 
"  Kerr,  Rep.  Med.  Off.  Education,  Lond.,  1907,  43. 
'  Simpson,  Rep.  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria 
to  Asylums  Bd.,  Lond.,  1898-99,  8. 

*  Cameron,  l^oport  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria 
to  Asylums  Bd.,  Lond.,  1901-02,  43. 

*  Turner,  Rep.  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria  to 
Asylums  Bd.,  Lond.,  1902-04,  3. 


82  THE  SOURCES  AND  MODES  OF  INFECTION 

United  States  in  the  year  ending  June  30,  1901,  the  fatality 
in  38,506  cases  was  only  1.79  per  cent.  At  such  a  time  great 
numbers  of  cases  escape  recognition.  The  patients  often 
have  no  idea  that  they  are  sick  with  a  dangerous  disease. 
They  may  be  at  their  work  even  during  the  prodromal  stage. 
There  may  be  only  half  a  dozen,  or  even  fewer,  atypical 
pustules.  I  have  in  rather  a  limited  experience  seen  several 
such  cases.  They  are  also  reported  by  Welch  and  Scham- 
berg.^  These  authors  also  state  that  cases  occur  where  there 
is  no  eruption  at  all.  The  step  from  half  a  dozen  points  of 
eruption  to  none  at  all  is  so  slight,  and  the  extremely  mild 
cases  at  times  are  so  numerous,  that  a  considerable  num- 
ber sine  eruptione  may  reasonably  be  expected.  Armstrong  ^ 
recently  reports  three  such  cases  with  some  fever  and  sub- 
jective symptoms  but  no  eruption.  They  occurred  in  infected 
families  and  subsequently  proved  refractory  to  vaccination. 

Measles. — There  is  little  clinical  evidence  that  "carriers" 
of  measles  are  common.  Most  health  officers  consider  that 
measles  is  rarely  carried  by  a  ''  third  person."  It  usually 
has  a  quite  definite  clinical  picture.  In  Aberdeen,  so  Dr. 
Matthew  Hay  writes  to  me,  judging  from  a  census  taken  in 
certain  schools,  it  was  estimated  that  from  90  to  93  per  cent 
of  the  children  over  ten  years  of  age  had  had  a  recognized 
attack  of  measles.  That  such  a  high  percentage  of  children 
had  recognized  attacks,  indicates  that  atypical  cases  cannot 
be  very  common.  Mild,  atypical  and  unrecognized  cases  of 
this  disease  must  be  far  less  numerous  than  are  such  cases 
in  scarlet  fever,  diphtheria  and  typhoid  fever. 

Protozoan  Diseases.  —  Although  the  marks  of  distinction 
between  animal  and  vegetable  life  as  seen  among  the  lower 
forms  are  ill  defined  and  uncertain,  yet  it  is  generally  agreed 
that  though  the  group  of  organisms  known  as  bacteria  have 
characters  belonging  to  both  the  vegetable  and  the  animal 
kingdom,  they  are  more  nearly  allied  to  the  former,  while  an- 

1  Welch  and  Schamberg,  Acute  Infectious  Diseases,  Phila.,  1905,  207. 
*  Armstrong,  Arch.  f.  Diagnosis,  1909,  II,  126. 


CARRIERS  AXD  MISSED  CASES  83 

other  group,  known  as  protozoa,  are  allied  to  the  lower  forms 
of  animal  life.  Although  one  of  the  latter  class  was  discovered 
to  be  the  cause  of  malaria  in  1880,  at  a  time  when  most  of  the 
disease-producing  bacteria  were  unknowTi,  the  bacteria  have 
received  far  more  study,  and  indeed  it  is  only  recently  that 
the  protozoa  as  the  cause  of  disease  have  received  much  atten- 
tion. It  is  knowm  that  a  number  of  diseases  both  of  men  and 
of  animals  are  caused  by  protozoa  of  various  types.  As  has 
recently  been  emphasized  by  Daniels,^  latency  is  a  common 
phenomenon  of  protozoan  infection,  and  is  of  the  utmost  im- 
portance from  an  epidemiological  standpoint.  Not  only  do 
the  blood  parasites  maintain  long  continued  infection  with 
few  symptoms,  but  such  forms  as  A?neba,  Balantidium,  and 
Lamblia  live  in  the  intestines  indefinitely,  reproducing  them- 
selves asexually.  A  number  of  the  diseases  to  be  referred  to 
do  not  affect  man,  but  they  serve  to  illustrate  the  prevalence 
of  latency  in  protozoan  infections. 

Texas  Cattle  Fever.  —  It  has  long  been  recognized  that 
the  Texas  fever  of  cattle  could  be  transmitted  by  apparently 
healthy  animals.  The  explanation  of  this  fact  was  not,  how- 
ever, forthcoming  until  Smith  and  Kilborne's^  classical  re- 
searches in  1893  demonstrated  that  the  disease  was  due  to 
a  blood  parasite,  a  protozoan  (Piroplasma  higeminum),  not  a 
bacterium,  and  also  demonstrated  that  it  is  only  transmitted 
from  animal  to  animal  by  means  of  a  species  of  tick  (Boophi- 
lus  annulatus),  in  which  the  parasite  passes  through  a  cycle 
of  changes  necessary  for  the  maintenance  of  the  species.  This 
work  of  Smith  and  Kill)orne's  was  one  of  the  most  important 
steps  in  the  dovelopnicnt  of  our  knowledge  of  the  insect 
carriage  of  disease,  a  knowledge  which  has  been  of  such  inesti- 
mable value  in  connection  with  malaria,  sleeping  sickness,  yel- 
low fever  and  other  blood  diseases.  It  wa«  soon  determined 
that  animals  which  had  recovered  from  Texas  fever  and  were 

•  Daniels,  Brit.  M.  J.,  Lond.,  1909,  II,  767. 

'  Smith  and  Kilborne,  U.  S.  Dept.  Agric,  liu.  An.  Ind.,  Bull.  No.  1, 
1893,  57. 


84  THE  SOURCES  AND  MODES  OF  INFECTION 

immune  to  it,  carried  the  piroplasma  in  the  blood  for  an 
indefinite  time.  In  one  instance  it  was  known  to  have  re- 
mained for  thirteen  years.^  Reports  from  the  PhiHppines^ 
show  that  many  of  the  cattle  in  those  islands  are  infected 
with  the  parasites  of  Texas  fever  though  showing  no  symp- 
toms. 

East  Coast  Cattle  Fever.  —  A  disease  much  like  our  Texas 
fever  is  known  as  East  Coast  African  cattle  fever.  It  is  due 
to  a  slightly  different  form  of  piroplasma  and  is  transmitted 
b}^  a  native  tick.  The  principal  source  of  infection  is  the 
native  animals  which  are  immune  and  whose  blood  contains 
the  organisms  of  the  disease.^ 

Malaria.  —  The  most  important  of  the  protozoan  diseases 
is  malaria.  It  had  always  been  believed  that  this  disease 
might  remain  latent  for  months  and  years,  but  what  latency 
really  meant  could  not  be  determined  until  after  the  dis- 
covery of  the  specific  cause  of  the  disease.  Many  of  the 
protozoa  pass  through  various  metamorphoses,  or  fixed  cycles 
of  development,  and  it  was  found  that  in  malaria  the  Plas- 
modium,  which  is  its  cause,  may  in  certain  stages  persist  in 
the  blood  or  organs  of  the  body  without  causing  any  charac- 
teristic symptoms,  or  indeed  any  symptoms  at  all.  Then  at 
any  time,  from  one  cause  or  another,  its  reproduction  may 
again  become  active  and  more  or  less  marked  symptoms 
appear.  Thus  relapses  may  occur  after  a  period  of  several 
years,  when  the  bodily  resistance  is  from  any  cause  impaired. 
Thus  fever  after  surgical  operation  is  not  rarely  due  to  a 
latent  malaria  becoming  active,  the  parasite  being  found  in 
the  blood  and  the  symptoms  yielding  to  quinia.  As  malaria 
is  a  strictly  transmissible  disease,  the  Plasmodium  which 
causes  it  being  borne  from  one  person  to  another  by  mosqui- 
toes, a  latent  case  of  the  kind  described  may  be,  and  doubt- 
less often  is,  the  means  of  introducing  the  disease  into  hitherto 

1  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  1904,  XXI,  26. 
^  Bull.  14,  Bu.  Gov.  Lab.,  Manila,  P.  I.,  1904,  11. 
»  Bruce,  Nature,  Lond.,  1905,  LXXII,  496. 


CARRIERS  AND   MISSED  CASES  85 

uninfected  localities.  Unless  such  cases  drift  into  hospitals, 
they  are  almost  certain  to  be  unrecognized.  Craig ^  made  a 
careful  study  of  424  such  latent  cases  found  among  165.3  sol- 
diers examined  in  the  Philippines.  Since  I  first  wrote  this 
chapter  Ciaig's  book  has  appeared  in  which  he  discusses  in 
much  detail  latency  and  recurrences.^  He  has  noted  an  asex- 
ual conjugation  of  the  parasites  in  the  blood  cells,  which  is 
followed  by  a  resting  stage,  and  which  he  believes  has  some 
relation  to  the  latency  of  the  infection.  Where  malaria  pre- 
vails extensively,  as  in  the  tropics,  it  has  long  been  noticed 
that  a  large  part  of  the  adult  population  is  immune.  It  is 
now  known  that  this  immunity  is  to  a  large  extent  acquired, 
and  is  due  to  the  invasion  of  the  body  in  infancy  by  the 
parasites.  This  invasion,  while  sometimes  causing  symptoms 
and  death,  frequently  gives  rise  to  few  or  no  symptoms,  or 
if  some  reaction  appears  at  first,  it  soon  disappears,  and  the 
children  may  seem  perfectly  well  though  the  parasites  are 
constantly  found  in  the  blood.  They  disappear  year  by  year 
and  infection  is  rarely  found  after  adolescence.  Koch^  in 
Africa  found  large  numbers  of  children  infected,  even  as  high 
as  100  per  cent.  Plehn^  found  many  adults  infected  though 
not  sick.  Christophers  and  Stephens  '  found  the  parasites  in 
the  blood  of  90  per  cent  of  infants  examined  in  one  locality 
on  the  Gold  Coast  in  Africa,  and  the  Thompson  Yates  ex- 
pedition to  Nigeria"  reports  finding  them  in  63  per  cent  of 
children  under  3  years  of  age.  Ziemann '  found  that  in  the 
Cameroon  country  37  per  cent  of  children  under  5  years  of 

»  Craig,  J.  Infect.  Dis.,  Chicago,  1907,  IV,  108. 

2  The  Mahirial  Fevers,  N.  Y..  1909,  228. 

3  Koch,  cited  in  Thompson  Yates'  Lab.  Rep.,  1900,  No.  4. 

*  Plehn,  cited  by  Marchiafava  and  Bignani,  Twentieth  Cent.  Prac- 
tice, XXI,  807. 

'  Christophers  and  Stephens,  Reports  of  the  Malarial  Commission  of 
the  Roy.  Soc.  (Eng.),  2nd  Ser.,  1900-03,  15. 

«  Thompson  Yates'  Lab.  Rep.,  19(X),  III,  Ft.  2,  201. 

'  Deutsche  med.  Wchnschr.,  1900,  XXVI,  399,  642,  753,  769. 


86  THE  SOURCES  AND  MODES  OF  INFECTION 

age  were  infected.  In  Panama  Kendall^  found  57  per  cent 
infected  of  the  natives  of  all  ages  examined  in  the  village 
of  Bahio,  and  73  per  cent  of  foreigners.  While  many  of 
the  latter  were  more  or  less  sick,  many  were  entirely  well. 
Darling'  in  villages  in  the  Panama  Canal  zone  where  there 
were  no  Anopheles,  nevertheless  found  that  10  per  cent  of 
the  laborers  at  work  were  infected  though  they  were  not  at 
all  sick.  Among  the  families  of  the  Spanish  and  the  West 
Indians,  the  latent  infection  reached  30  per  cent.  It  is  this 
latent  infection  in  the  blood  of  the  native  population  which 
is  the  cause  of  the  malaria  which  so  certainly  attacks  arrivals 
from  non-malarial  regions.  The  greater  the  distance  that  can 
be  placed  between  the  natives  and  the  strangers  the  less 
the  danger  of  the  latter  contracting  the  disease. 

Sleeping  Sickness.  —  African  sleeping  sickness  has  been 
shown  to  be  due  to  a  protozoan,  Trypanosoma  gambiense. 
This  disease  has  been  much  studied  of  late,  and  it  seems  cer- 
tain that  it  is  transmitted  by  means  of  the  tsetse  fly  (Glossina 
palpalis),  though  whether  it  is  a  purely  accidental  mechanical 
transference  on  the  proboscis  of  the  fly,  or  whether  it  passes 
through  a  part  of  its  life  history  in  the  body  of  the  fly,  as 
the  Plasmodium  of  malaria  does  in  the  mosquito,  is  still  uncer- 
tain. In  any  event  the  parasite  is  frequently  found  in  the 
blood  of  apparently  healthy  subjects,  just  as  is  the  malarial 
parasite.  According  to  Todd  ^  it  may  remain  in  the  blood 
for  15  years,  causing  no  symptoms,  and  frequently  remains 
for  many  months.  The  expedition  from  the  Liverpool  School 
of  Tropical  Medicine*  found  many  natives  infected,  but  who 
exhibited  no  symptoms,  or  only  slight  symptoms.  The  greater 
the  prevalence  of  the  disease  the  more  common  are  these 
latent  cases.    In  Gambia,  where  the  disease  is  rare,  not  more 

'  Kendall,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVI,  1151,  1266. 

2  Darling,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  2051. 

3  Todd,  Tr.  Epidemiol.  Soc,  Lond.,  1905-06,  XXV,  1. 

*  Liverpool  School  Trop.  Med.  Memoirs,  1904,  XIII;  Med.  News, 
N.  Y.,  1904,  LXXXV,  526,  615. 


CARRIERS  AND   MISSED  CASES  87 

than  one  native  in  1000  examined  showed  the  parasites,  while 
in  the  Congo  46  in  100  were  infected,  and  in  Uganda  the 
percentage  was  still  higher.  Whether  the  disease  is  always 
transferred  from  man  to  man,  or  whether  some  of  the  lower 
animals  also  harbor  the  parasites  and  thus  serve  as  a  "reser- 
voir "  from  which  the  human  disease  is  derived,  is  as  yet 
uncertain. 

Nagana.  —  Nagana'  is  an  African  cattle  disease  which, 
like  the  sleeping  sickness,  is  caused  by  a  trypanosome  T. 
brucei,  and  is  also  transmitted  by  a  tsetse  fly,  G.  viorsitans, 
though  of  another  species.  Wild  herbivora  are  very  generally 
infected  with  the  specific  trypanosome  of  this  disease,  but 
because  of  immunity,  probably  acquired,  they  show  few  or 
no  symptoms.  These  carriers  are  the  real  source  of  the 
disease  which  .so  speedily  attacks  imported  animals. 

Syphilis.  —  The  spirochete  of  syphilis  has  in  one  instance 
been  reported  as  remaining  latent  in  a  healed  lesion  of  that 
disease." 

Amebic  Dysentery.  —  There  are  two  forms  of  dysentery, 
one  caused  by  a  bacillus  and  the  other  due  to  an  ameba. 
The  amebic  form  has  been  carefull}'  studied  by  Musgrave 
and  Clegg  ^  in  the  Philippines.  These  authors  are  inclined 
to  think  that  many  of  the  amebae  which  are  widely  dissemi- 
nated in  the  Philippines  are  pathogenic  for  man.  They  may, 
however,  often  remain  in  the  intestines  for  months  without 
causing  symptoms.  They  found  amebse  in  101  of  300  pris- 
oners. Of  thes(!  Gl  had  had  dysentery,  40  gave  no  history 
of  dysentery,  but  of  the.se  8  died  of  intercurrent  affections, 
and  dysenteric  lesions  were  found  in  all.  Of  32  others,  30 
later  developed  dysentery,  and  2  passed  from  ob.servation. 
These  authors  quote  Celli  and  Fiocca,  Strong  and  Musgrave, 

'  Minchin,  Gray  and  Tullock,  Proc.  Roy.  Soc,  Lond.,  1906;  Nature, 
Lond.,  19()(),  LXXVII,  ')! . 

'  Pa.sirii,  quoted  by  Rosenberger,  N.  York  M.  J.  [etc.],  1908, 
LXXXVII,  394. 

'  Musgrave  and  Clegg,  J.  Infect.  Dis.,  Chicago,  1905,  II,  334. 


88  THE  SOURCES  AND  MODES  OF  INFECTION 

Cunningham,  and  Grassi  as  also  finding  amebse  in  healthy 
persons. 

Percentage  of  Carriers  of  Amebae.  —  Walker  ^  found  70 
per  cent  of  50  native  soldiers  in  the  Philippines  infected  with 
amebse,  and  50  per  cent  of  50  American  soldiers,  though  they 
were  not  sick  with  dysentery.  Garrison  ^  reports  that  23  per 
cent  of  4106  prisoners  in  the  Philippines  had  amebae  in  their 
stools.  Hoyt  ^  examined  the  feces  of  280  hospital  patients, 
medical,  surgical  and  venereal,  and  found  amebse  in  84,  or 
30  per  cent.  Craig,^  however,  does  not  agree  with  Musgrave 
and  Clegg,  and  Walker,  but  believes  with  Schaudinn  that 
the  ameba,  Entameha  coli,  so  frequently  found  in  healthy  per- 
sons, is  a  different  species  from  E.  histolytica,  which  is  found 
only  in  cases  of  dysentery  or  in  convalescents.  This  is  also 
the  view  of  Vedder.^  Even  if  the  contention  of  these  latter 
authors  is  correct,  and  most  of  the  intestinal  amebse  that 
are  so  commonly  found  in  the  tropics  are  distinct  from  the 
true  dysentery  ameba,  it  is  certain  that  the  latter  is  some- 
times found  in  persons  for  a  long  time  after  recovery,  and 
may  also  be  found  in  the  feces  before  the  disease  develops. 
Martini  ®  reports  a  case  in  which  the  sickness  lasted  from  the 
15th  of  September  to  the  1st  of  December,  1907,  but  in  which 
the  amebse  persisted  until  the  last  of  January,  1908.  Vin- 
cent ^  reports  several  instances  in  which  persons  were  carriers 
for  five  months  after  their  return  to  France  from  Tonkin. 
Lemoine^  had  under  observation  a  man  who  contracted  the 
disease  in  China  in  1897  and  returned  to  France  and  trans- 

'  Walker,  J.  Med.  Research,  Bost.,  1907-08,  XVII,  379. 
^  Garrison,  Philippine  J.  So.,  Manila,  1908,  III,  200. 
3  Hoyt,  Philippine  J.  Sc,  Manila,  1908,  III,  417. 

*  Craig,  J.  Infect.  Dis.,  Chicago,  1908,  V,  324. 

6  Vedder,  J.  Am.  M.  Ass.,  Chicago,  1906,  XLVI,  870. 

«  Martini,  Arch.  f.  Schiffs-  u.  Tropen-Hyg.,  Cassel,  1908,  XII,  588. 

^  Vincent,  Bull.  Soc.  path,  exot..  Par.,  1909,  II,  78. 

*  Lemoine,  Bull,  et  mem.  Soc.  med.  d.  hop.  de  Par.,  1908,  3d  Sen, 
XXV,  640. 


CARRIERS  AND  MISSED  CASES  89 

mitted  the  disease  to  another  in  1908.  It  seems  probable 
that  the  cases  which  are  occasionally  noted  in  the  northern 
United  States  are  due  to  contact  in  some  way  with  chronic 
carriers  returned  from  the  tropics. 

Yellow  Fever.  —  The  parasite  which  is  the  cause  of  yellow 
fever  is  still  unknown,  although  fortunately  for  preventive 
medicine  we  have  very  accurate  knowledge  of  the  manner 
in  which  the  disease  is  transmitted.  As  in  scarlet  fever,  so  in 
yellow  fever,  lack  of  knowledge  of  the  parasite  renders  diffi- 
cult the  recognition  of  carrier  cases  if  they  exist.  But  there 
is  abundant  clinical  evidejice  that  many  very  mild  and  atyp- 
ical cases  occur  which  it  is  impossible  to  recognize.  It  is  in 
young  children  chiefly  that  this  slight  disturbance  is  produced 
by  the  infection.  A  similar  phenomenon  is  noted  in  malarial 
disease,  and  young  children  are  the  chief  source  of  infection 
in  both  yellow  fever  and  malaria.  The  fact  of  the  mildness 
of  these  cases,  their  frequency,  and  the  impossibility  of  mak- 
ing a  diagnosis,  has  been  insisted  upon  by  Finlay,  Gorgas, 
Guiteras,  Carter,  Agramonte,  Marchoux  and  others.  Brady  ^ 
states  that  the  fatality  among  children  is  sometimes  as  low 
as  0.5  per  cent.  Even  in  adults,  walking  cases,  which  it  is 
impossible  to  discover  by  an  ordinary  examination,  are  not 
rare.  Thus  it  was  claimed  that  during  an  outbreak  in  Louisi- 
ana a  single  walking  case  carried  the  disease  to  three  different 
communities.  Quarantine  officers  now  take  the  temperature 
of  each  passenger,  and  in  this  way  yellow  fever  cases  are 
occasionally  detected  which  would  otherwise  have  walked 
ashore  without  exciting  suspicion.^ 

Conclusions.  —  We  are  justified  from  the  evidence  pre- 
sented in  coming  to  the  following  conclusions: 

1.  Mild  atypical  and  unrecognized  cases  of  the  infectious 
diseases  are  often  extremely  common.  In  many  diseases  they 
may  be  more  numerous  than  the  recognized  eases. 

2.  Disease-producing   micro-organisms,    whether  bacteria 

»  Brady,  N.  Orl.  M.  &  S.  J.,  1905-06,  LVIII,  550. 

»  Doty,  Am.  Pub.  Health  Ass.  Rep.,  1905.  XXXI,  Pt.  I,  261. 


90  THE  SOURCES  AND  MODES  OF  INFECTION 

or  protozoa,  frequently  persist  in  the  body  without  causing 
symptoms. 

3.  Sometimes  the  germs  remain  only  a  few  weeks  or  months 
after  convalescence,  and  sometimes  they  may  persist  for 
years,  perhaps  for  life.  Sometimes  these  carriers  give  no 
history  of  ever  having  been  sick. 

4.  While  the  bacteria  found  in  carriers  are  sometimes  lack- 
ing in  virulence,  many  times  they  show  the  highest  degree 
of  virulence. 

5.  There  is  ample  epidemiological  evidence  that  healthy 
carriers  as  well  as  mild  unrecognized  cases  are  the  source  of 
well-marked  outbreaks. 

6.  The  number  of  carriers  varies  greatly  in  different  dis- 
eases. From  20  to  50  per  cent  of  the  population  are  carriers 
of  pneumococci.  It  seems  probable  that  the  influenza  bacillus 
is  as  widely  distributed.  During  outbreaks  of  cerebro-spinal 
meningitis  the  number  of  carriers  may  be  from  10  to  30  times 
as  numerous  as  the  number  of  cases.  Even  when  diphtheria 
is  not  prevalent  1  per  cent  of  the  population  may  be  carrying 
the  bacilli,  and  during  outbreaks  the  number  may  be  several 
times  greater.  Probably  25  per  cent  of  all  typhoid  fever  cases 
excrete  bacilli  for  some  weeks  after  convalescence,  and  it  is 
estimated  that  from  1  in  500  to  1  in  250  of  the  population 
are  chronic  carriers.  What  little  evidence  there  is  indicates 
that  carriers  are  as  numerous  in  dysentery  and  cholera  as 
they  are  in  typhoid  fever.  In  yellow  fever,  sleeping  sickness, 
and  particularly  in  malaria,  carriers  are  very  numerous. 
There  is  no  evidence  that  there  are  many  carriers  of  measles 
or  smallpox. 

7.  Any  scheme  of  prevention  which  fails  to  take  into  ac- 
count carriers  and  missed  cases  is  doomed  to  partial  and 
perhaps  complete  failure. 


CHAPTER  III. 

LIMITATIONS    TO    THE    VALUE    OF   ISOLATION. 

Number  of  Mild  Cases  and  Carriers.  —  In  the  first  chapter 
the  attempt  was  made  to  show  that  pathogenic  organisms  do 
not  usually  develop  outside  of  the  body.  Except  for  a  few 
diseases,  or  under  unusual  circumstances,  the  saprophytic 
existence  of  disease  germs  is  not  to  be  looked  for.  Such 
sources  of  infection  are  much  rarer  than  is  generally  assumed, 
and  for  most  diseases  may  be  entirely  neglected.  In  the 
second  chapter,  evidence  was  presented  that  certain  other 
sources  of  infection  are  very  much  more  numerous  than  is 
generally  believed,  and  it  is  here  contended  that  no  scheme 
of  sanitation  can  have  a  scientific  basis,  or  can  have  any 
possibiHty  of  success,  which  does  not  take  full  cognizance  of 
them. 

It  must  be  admitted  by  all  that  mild  atypical  cases  of  con- 
tagious diseases  are  very  numerous.  Every  one  who  has  had 
any  experience  with  the  last  epidemic  of  smallpox  in  the 
United  States  and  England  must  have  had  many  unpleasant 
reminders  of  this.  Health  officers'  reports  are  full  of  instances 
of  the  introduction  of  the  disease  into  a  community  by  per- 
sons unsuspected  by  any  one  of  having  the  disease,  and  who 
often  give  rise  to  a  whole  series  of  cases.  Similar  experiences 
with  scarlet  fever  are  often  reported.  The  most  critical  inves- 
tigation, such  as  that  of  our  surgeons  in  the  Spanish  War, 
indicates  that  mild  unrecognized  cases  of  typhoid  fever  fully 
equal,  if  they  do  not  exceed,  the  number  of  cases  which 
are  recognized  and  reported.  Even  with  every  facility  for 
diagnosis,  the  amount  of  sore  throat  due  to  the  diphtheria 
bacillus,  but  not  so  suspected,  is  fully  equal  to  the  amount 
of   recognized    diphtheria;    and   in   many  other   infectious 

91 


92  THE  SOURCES  AND  MODES  OF  INFECTION 

diseases  these   mild    cases  occur  with  varying   degrees  of 
frequency. 

Usually  not  Recognized.  —  The  extent  to  which  these  mild 
atypical  cases  escape  recognition  varies  with  the  disease,  the 
social  condition  of  the  people  affected,  the  intelligence  and 
conscientiousness  of  the  physician,  and  the  attitude  of  the 
health  officer.  That  the  majority  of  people  will  not  consult 
a  physician  unless  they  are  decidedly  sick,  is  certain.  That 
they  will  refrain  from  doing  so  if  they  expect  to  be  reported 
to  the  health  officer  and  to  be  placed  under  various  restric- 
tions, is  but  in  accord  with  human  nature.  A  slight  sore 
throat,  or  a  fleeting  rash,  little  suggestive  of  danger,  will  be 
lightly  passed  over,  no  physician  will  be  called  and  no  pre- 
cautions taken,  and  often  there  will  be  no  thought  of  danger 
to  others.  It  has  always  been  known  that  a  certain  number 
of  mild  cases,  difficult  to  recognize,  could  be  expected  in 
almost  all  infectious  diseases,  but  it  remained  for  the  labora- 
tory worker  to  show  how  numerous  they  are  in  such  diseases 
as  typhoid  fever,  diphtheria,  plague  and  malaria.  The  micro- 
scopic demonstration  of  the  frequency  with  which  clinically 
unrecognizable  attacks  of  the  above  named  and  other 
diseases  occur,  had  called  the  attention  of  clinicians  and  epi- 
demiologists to  their  probable  occurrence  in  such  other  dis- 
eases as  scarlet  fever,  smallpox,  and  yellow  fever,  the  specific 
organisms  of  which  have  not  as  yet  been  discovered.  So  that 
at  the  present  time  the  most  careful  epidemiologists,  clinicians 
and  laboratory  workers  begin  to  realize  that  very  large  num- 
bers of  mild  atypical  and  unrecognizable  cases  are  bound  to 
occur  in  most  infectious  diseases.  But  as  j^et  few  text-books 
on  sanitation,  clinical  medicine,  or  even  on  bacteriology,  lay 
sufficient  emphasis  on  this  fact.  Nothing  is  more  common 
than  to  find  the  young  man  just  from  the  medical  school,  as 
well  as  the  old  practitioner,  quick  to  deny  the  presence  of 
scarlet  fever,  diphtheria,  or  typhoid  fever  because  the  symp- 
toms are  not  severe  enough  or  because  they  deviate  too 
much  from  the  text-book  description.    But  the  large  number 


LIMITATIONS   TO    THE   VALUE  OF  ISOLATION        93 

of  the  mild  and  aberrant  cases,  which  usually  remain  "missed 
cases,"  and  their  importance  in  the  extension  of  the  infectious 
diseases,  must  now  be  admitted. 

Carriers  Exceedingly  Numerous.  —  Still  more  numerous 
are  the  pure  carriers,  those  persons  in  whose  bodies  the 
pathogenic  bacteria  and  protozoa  develop  without  causing 
symptoms.  The  recognition  of  this  element  of  danger  is  due 
entirely  to  laboratory  investigation,  but,  strange  to  say,  most 
workers  on  bacteriology  lay  no  more  stress  on  this  epidemio- 
logical factor  than  do  the  writers  of  treatises  on  hygiene  or 
of  text-books  of  medicine.  In  the  preceding  chapter  sufficient 
evidence  was  presented  to  demonstrate  the  very  great  fre- 
quency with  which  these  carrier  cases  occur.  Their  exist- 
ence and  the  virulence  of  the  germs  which  they  carry  are 
now  established  facts.  Numerous  instances  were  given  where 
such  carriers  appeared  to  have  transmitted  the  disease  to 
others.  Indeed  it  is  almost  inconceivable  that  it  should  be 
otherwise.  It  is  hardly  possible  that  virulent  typhoid  bacilli 
or  diphtheria  bacilli  produced  in  large  numbers,  as  they  fre- 
quently are  in  carriers,  should  not  be  equally  as  dangerous  as 
those  which  develop  in  the  bodies  of  the  sick.  That  is,  they 
are  equally  dangerous  potentially;  actually  the  well  person 
moving  freely  about  may  be  more  dangerous  to  the  com- 
munity than  the  sick  person  who  is  confined  to  the  house. 

Approaching  the  subject  from  another  standpoint,  it  is 
interesting  to  see  how  the  discovery  of  these  missed  and  car- 
rier cases  has  explained  so  much  which  we  formerly  did  not 
understand. 

Effort  to  "  Stamp  Out  "  Disease,  —  Twenty-five  or  thirty 
years  ago  we  heard  a  great  deal  about  "stamping  out"  the 
contagious  disea.ses.  That  was  the  era  of  the  building  of  hos- 
pitals for  these  diseases,  of  the  organization  of  the  sanitary 
service,  of  the  discovery  of  pathogenic  bacteria.  The  wonder- 
ful decrease  in  smallpox,  the  successful  fight  against  cholera, 
the  almost  total  disappearance  of  typhus  fever,  and  the  com- 
plete disappearance  of  plague,  only  foreshadowed,  it  was  said, 


94         THE  SOURCES  AND  MODES  OF  INFECTION 

the  extermination  of  typhoid  fever,  diphtheria,  scarlet  fever 
and  measles.  It  was  claimed  that  in  those  diseases  which 
are  exclusively  contagious,  if  every  case  can  be  isolated  until 
it  is  free  from  infection,  the  disease  will  be  exterminated.  It 
was  believed  that  if  people,  and  especially  physicians,  would 
take  only  a  little  more  care,  practically  all  cases  of  these 
diseases  could  be  recognized  and  isolated.  It  was  also  thought 
to  be  not  very  difficult  to  control  them  until  infection  had 
disappeared.  This  confidence  in  the  efficacy  of  isolation  was 
in  the  then  existing  state  of  knowledge  not  unreasonable. 

Isolation  and  its  Results  in  Providence.  —  Previous  to 
1884  there  had  been  in  Providence  no  isolation  to  speak  of 
in  any  of  the  contagious  diseases  except  smallpox.  In  fact 
very  many  physicians  did  not  consider  that  scarlet  fever  and 
diphtheria  were  very  contagious,  if  contagious  at  all,  but 
were  inclined  to  look  upon  them  as  filth  diseases.  Restric- 
tive measures,  including  isolation  at  home  and  fumigation, 
began  to  be  applied  in  1884  and  were  quite  steadily  strength- 
ened during  the  next  sixteen  or  seventeen  years.  I  hoped, 
as  did  most  health  officers,  that  if  scarlet  fever  and  diph- 
theria could  not  be  stamped  out,  they  could  be  reduced  to 
an  insignificant  remnant.  But  they  were  not  stamped  out 
in  Providence,  as  they  have  not  been  in  other  cities.  On  the 
contrary,  we  had  twice  as  many  deaths  in  1887  from  scarlet 
fever  as  we  had  had  during  any  year  for  seven  years.  Diph- 
theria from  1886  to  1890  also  caused  nearly  double  the  num- 
ber of  deaths  that  it  had  in  the  preceding  four  years.  Of 
course  we  talked  about  epidemic  waves,  and  noted  that  the 
mortality  from  the  last  wave  was  very  much  lower  than  from 
many  that  had  preceded  it,  and  congratulated  ourselves  that 
the  outbreak  was  not  so  severe  as  in  former  years.  But  I 
began  to  ask  myself  what  there  was  about  epidemic  waves 
that  made  restrictive  measures  of  little  use,  and  also  to  inquire 
if  there  was  anything  wrong  about  the  restrictive  measures. 
If  we  were  limiting  these  diseases  at  all,  it  was  certainly  in  a 
very  moderate  way. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION        95 

Infection  by  Air  and  Fomites  Thought  Most  Important.  — 
It  vvas  fully  appreciated  that  in  cities  at  least  most  cases 
of  contagious  disease  cannot  be  traced  to  their  source.  Two 
theories  have  from  antiquity  been  advanced  in  explanation. 
One  is  that  most  contagious  diseases  are  easily  carried 
by  the  atmosphere.  Thus  a  person  going  by  a  house  where 
there  is  scarlet  fever,  or  passing  an  infected  person  in  the 
street,  might  contract  the  disease.  Such  unconscious  exposure 
might  be  quite  common.  But  the  principal  source  of  the 
untraced  cases  of  contagious  disease  was  believed  to  be  fo- 
mites. Walls  and  furniture  were  thought  to  become  infected 
with  the  virus,  and  for  weeks  and  months  persons  entering 
the  room  might  contract  disease  through  the  breath.  Books, 
toys,  clothing  and,  in  fact,  every  material  thing,  might  readily 
become  a  source  of  infection  and  retain  its  virulence  for 
months  and  years.  These  were  perhaps  not  unreasonable 
a  priori  hypotheses,  and  they  had  some  apparent  backing  of 
facts.  At  any  rate  they  were  the  best  theories  we  had.  So 
health  officers  everywhere,  including  Providence,  set  about 
improving  methods  of  disinfection.  Sulphur  fumigation  was 
abandoned  and  the  use  of  formaldehyde  gas  adopted  in 
its  place.  Many  cities  set  up  a  steam  disinfecting  plant,  in 
Providence  as  early  as  1887,  and  carpets,  bedding  and  cloth- 
ing were  disinfected  by  steam.  Some  cities,  particularly  on' 
the  continent  of  Europe,  sent  a  band  of  uniformed  disinfec- 
tors  to  wash  and  scrub  everything  in  the  infected  house. 
Scarlet  fever  and  diphtheria  refused  to  be  exterminated, 
though  in  Providence  we  did  have  rather  less  during  the  early 
nineties  than  we  had  had  before.  But  I  was  not  satisfied. 
It  seemed  to  me  that  we  were  having  too  much  of  these 
diseases,  that  there  must  be  a  leak  somewhere. 

Cultures  Expected  to  Discover  Much  Diphtheria.  —  Then 
for  one  disea.se  a  now  weapon  was  i)ut  into  our  hands.  Many 
had  long  recognized  that  the  diagnosis  of  diphtheria  was  diffi- 
cult. It  was  suspected  that  many  cases,  because  of  this  diffi- 
culty, escaped  isolation  entirely.     When  the  culture  method 


96  THE  SOURCES  AND  MODES  OF  INFECTION 

of  diagnosis  was  devised  I  became  enthusiastic  and  hopeful. 
We  adopted  it  in  Providence  in  January,  1895,  and  soon  after 
required  a  negative  culture  before  the  patient  was  released 
from  isolation.  Hill  has  shown  that  without  cultures  the 
chance  of  error  in  the  diagnosis  of  diphtheria  is  50  per  cent, 
which  corresponds  entirely  with  my  frequently  expressed 
opinion  before  the  advent  of  the  culture  method.  It  is  evi- 
dent, then,  that  the  general  use  of  cultures  ought  to  bring  to 
light  great  numbers  of  cases  of  diphtheria  which  were  formerly 
unrecognized,  and  this  it  certainly  does.  If  such  an  im- 
provement in  diagnosis,  and  consequently  in  isolation,  is 
brought  about  by  the  use  of  cultures,  and  if  by  the  same  means 
isolation  can  be  maintained  until  the  patient  is  certainly  free 
from  infection,  there  ought  to  follow  a  marked  reduction 
in  this  disease.  But  it  was  quite  otherwise.  The  deaths  in 
Providence,  which  in  1894  had  numbered  45,  rose  to  79  in 
1895  and  125  in  1896,  nearly  twice  as  many  in  proportion  to 
the  population  as  there  were  in  1883,  when  there  was  no  isola- 
tion, no  disinfection  and  no  antitoxin.  The  cases  rose  from 
166  in  1894  to  386  in  1895  and  890  in  1896.  The  apparent 
reduction  in  the  fatality  rate  from  27.71  to  14.07  indicates 
very  plainly  that  the  culture  method  of  diagnosis  had  dis- 
covered a  very  large  number  of  mild  cases  that  would  have 
previously  been  unrecognized,  for  antitoxin  was  only  a  minor 
factor  in  reducing  the  fatality,  as  it  had  been  used  in  only  a 
little  over  one-third  of  the  cases.  Isolation,  disinfection,  the 
use  of  cultures,  and  the  opening  of  the  contagious  hospital 
had  been  accompanied  by  the  greatest  prevalence  of  the  dis- 
ease for  ten  years.  I  do  not  mean  to  say  that  the  adoption 
of  the  measures  described  had  no  effect  upon  the  amount 
of  diphtheria  in  Providence.  I  am  sure  that  they  had,  and 
that  this  disease  on  the  whole  has  been  lessened,  cases  pre- 
vented and  lives  saved.  But  better  results  were  expected. 
I  was  disappointed,  and  I  think  other  health  officers  have 
been  disappointed  also.  It  seemed  that  the  measures,  car- 
ried out  as  they  were,  ought  to  have  given  better  results. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION        97 

It  seemed  that  there  was  something  which  we  did  not 
understand. 

Failure  of  Hospital  Isolation.  —  One  of  the  most  effectual 
means  of  isolating  cases  of  contagious  diseases  is  by  removal 
to  the  hospital.  Certainly  while  in  the  hospital  they  can  do 
no  harm,  and  with  reasonable  care  there  is  not  much  danger 
of  their  carrying  infection  back  to  their  homes.  Return  cases 
do  not  occur  in  scarlet  fever  and  diphtheria  in  more  than 
about  one  to  three  per  cent  of  discharges,  and  are  not  a  factor 
of  moment  in  the  extension  of  these  diseases.  The  idea  that 
such  hospitals  would  be  a  powerful  factor  in  the  extermina- 
tion of  these  diseases  was  not  unreasonable.  Smallpox  hos- 
pitals have  been  in  general  use  for  a  very  long  time,  but  they 
are  not  here  under  consideration,  though  it  is  questionable 
whether  the  hospital  isolation  of  smallpox  can  ever  accom- 
plish much  alone  and  unaided  by  vaccination.  But  it  is  the 
hospitalization  of  scarlet  fever  and  diphtheria  that  is  par- 
ticularly instructive. 

English  Hospitals.  —  The  use  of  hospitals  for  contagious 
diseases  has  been  carried  farther  in  England  than  elsewhere. 
Fifteen  or  twenty  years  ago  the  larger  nmnicipalities  began 
building  them  on  a  considerable  scale,  and  at  present  most 
of 'the  English  towns  are  provided  with  large  hospitals  for 
scarlet  fever,  and  to  a  less  extent  for  diphtheria.  At  the  time 
when  their  construction  was  first  strongly  urged  it  was  be- 
lieved that  their  use  would  result  in  the  eradication  of  the 
diseases  for  which  they  were  provided.  The  result  has  cer- 
tainly been  disappointing,  and  there  has  recently  been  an 
active  discussion  as  to  whether  they  do  an  amount  of  good  in 
restricting  disease  at  all  commensurate  with  their  cost.'  There 
is  no  doubt  that  the  mortality  from  scarlet  fever,  both  in 

'  O'Connor,  Geo.  Wilson,  Waddy  and  others,  Brit.  M.  J.,  I>ond.,  1905, 
II,  6.30;  Millard,  Bi.ss,  Fraser,  etc.,  Med.  Pros.s  <t  Cirr.,  Ix)nd.,  l<)Ot, 
LXXVIII,  21."),  21S,  241,  327,  377;  Nowsholine,  Tr.  Epidcin.  Soe. 
Lond.,  n.  s.,  1900-01,  XX,  48;  J.  IlyK-,  1901,  I,  14.');  Millard,  Piil). 
Health,  1901,  XIII;  J.  T.  Wilson,  Pub.  Health,  1896-97,  IX,  Sup.,  p.  21. 


98  THE  SOURCES  AXD  MODES  OF  INFECTION 

England  and  the  United  States,  has  greatly  diminished  during 
recent  years,  but  whether  this  has  been  due  to  restrictive 
measures  or  to  lowered  virulence  has  been  disputed.  The 
small  death  rate  would  indicate  that  the  disease  is  really 
milder.  This  is  also  indicated  by  the  fact  that  plural  deaths, 
that  is,  more  than  one  death  in  a  family,  are  less  frequent 
now  than  formerly.  Again,  local  outbreaks  of  the  old-time 
severe  type  occasionally  appear.  There  was  such  an  out- 
break in  Providence  in  1906-07,  during  which  the  case  fatal- 
ity ran  up  to  12.85  per  cent.  Similar  outbreaks  have  been 
noted  in  Keene,  N.  H.,  Haverhill,  Worcester  and  Mont- 
real. The  relatively  lowered  fatality  in  recent  years  has 
rendered  it  difficult  to  determine  from  the  number  of  deaths 
just  what  influence  restrictive  measures,  like  hospital  isola- 
tion, have  had  on  the  prevalence  of  scarlet  fever,  and  increas- 
ing accuracy  and  care  in  reporting  cases  render  it  difficult 
to  draw  conclusions  from  the  number  of  cases.  But  after 
all  has  been  said  it  is  clear  that  hospital  isolation  in  scarlet 
fever  has  checked  the  disease  very  much  less  than  was  ex- 
pected, and  sometimes  appears  to  have  had  little  effect.  In 
Huddersfield,  a  city  of  nearly  one  hundred  thousand  people, 
from  1890  to  1899  the  percentage  of  removals  to  the  hospital 
was  90,  yet  the  mean  attack  rate  for  the  period  was  4.3  per 
thousand.  From  1900  to  1908  the  removals  to  the  hospital 
were  92.4  per  cent  and  the  attack  rate  2.96.  This  is  certainly 
a  surprisingly  high  morbidity  rate  for  a  city  where  practically 
all  reported  cases  have  for  twenty  years  been  subjected  to 
most  excellent  isolation.  A  similar  state  of  things  is  noted 
in  other  cities.  Some  cities  with  a  high  per  cent  of  removals 
to  the  hospital  have  more  of  the  disease  than  do  cities  with 
no  hospitals.  The  same  is  noted  in  rural  communities. 
O'Connor,^  medical  officer  of  health  of  Leicestershire  and  Rut- 
land combined  sanitary  districts,  reported  that  in  five  par- 
ishes where  the  percentage  of  hospital  isolation  had  for  ten 
years  reached  66  per  cent,  the  attack  rate  was  6.2  per  thou- 
'  O'Connor,  Brit.  M.  J.,  Lend.,  1905,  II,  630. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION        99 

sand,  while  in  five  other  parishes  where  hospital  isolation  was 
applied  to  only  14  per  cent  of  the  cases,  the  attack  rate  was 
2.8.  In  another  district,  one  parish  which  sent  60  per  cent  of 
its  scarlet  fever  to  the  hospital,  had  three  times  as  many 
cases  as  contiguous  parishes  which  had  little  hospital  isola- 
tion. Neech^  says  that  in  Cornwall  from  1898  to  1907  there 
was  practically  no  difference  in  the  incidence  of  scarlet  fever, 
in  both  urban  and  rural  districts,  connected  with  the  use  or 
failure  to  use  isolation  hospitals.  Again,  a  city  after  it  builds  a 
hospital  may  have  more  of  the  disease  than  before.  The  aban- 
donment of  hospital  isolation  may  do  no  harm.  In  Leices- 
ter^ the  hospital  was  closed  temporarily,  and  all  the  scarlet 
fever  cases  sent  to  their  homes,  with  an  actual  decrease  in 
number  of  reported  cases.  The  hospital  in  other  cities  also 
has  been  closed  without  harm.  I  have  thought  it  possible 
that  at  times  hospital  isolation  might  actually  favor  the 
spread  of  disease.  When  a  case  is  removed  to  the  hospital, 
comparatively  little  restraint  is  placed  upon  other  members 
of  the  family,  and  if  some  of  them  are  carriers,  as  they  cer- 
tainly usually  are  in  diphtheria,  much  harm  may  result.  If, 
however,  the  case  is  kept  at  home,  the  rest  of  the  family, 
particularly  the  children,  are  under  considerable  restraint  for 
several  weeks.  Observations  in  Providence  demonstrate  that 
the  retention  of  the  case  at  home  very  rarely  leads  to  the 
extension  of  the  disease  to  other  families  in  the  house,  and 
presumably  to  still  less  extension  outside  of  the  house. 

Why  the  Failure  ?  —  It  may  be  admitted,  and  is  doubtless 
true,  that  hospitals  have  prevented  very  many  cases  of  dis- 
ease, and  they  may  have  been  somewhat  of  a  factor  in  its 
lessened  prevalence.  Nevertheless  it  must  also  bo  admitted 
that,  notwithstanding  the  complete  and  excellent  isolation 
secured  in  some  cities  like  Huddersfield,  scarlet  fever  has 
still  prevailed  to  an  alarming  extent.  When  eighty  to  ninety 
per  cent  of  the  cases  are  removed  to  the  hospital  it  is  certain 

'  Neech,  Pub.  Health,  Lond.,  1908-09,  XXII,  296. 
^  Rep.  on  Health  of  Leicester,  1902,  36. 


100        THE  SOURCES  AND  MODES  OF  INFECTION 

that  the  remainder  will  be  so  situated  that  home  isolation  will 
quite  effectually  prevent  extension  from  them.  In  such  cities 
almost  all  of  the  reported  cases  are  thus  effectively  isolated, 
either  in  hospital  or  home.  Yet  the  disease  continues  to  pre- 
vail. There  is  evidently  some  source  which  escapes  control. 
Newsholme  has  very  clearly  shown  this.  While  admitting 
that  isolation  does  prevent  much  sickness,  he  says  that  the 
disease  still  prevails  and  outbreaks  still  occur  owing  to  some 
"epidemic  influence."  Now  our  purpose  is  to  determine,  if 
possible,  what  this  "epidemic  influence"  is.  What  is  the 
factor  which  is  so  powerful  and  continuous  in  its  action  that 
90  to  95  per  cent  of  perfection  in  the  isolation  of  a  contagious 
disease  is  unable  to  prevent  a  continued  high  prevalence  and 
repeated  epidemic  waves  ? 

American  Hospital  Experience.* —  It  is  not  merely  English 
hospital  experience  which  has  shown  the  inefficiency  of  isola- 
tion. We  have  numerous  instances  in  our  own  country.  I 
have  already  referred  to  the  experience  of  Providence,  where 
increasing  stringency  in  isolation  was  not  followed  by  a 
decrease  in  contagious  diseases.  There  has  been  much  dif- 
ference between  American  cities  as  regards  the  strictness  of 
enforced  isolation.  Some  have  been  notoriously  lax,  while 
others  have  for  years  endeavored  to  secure  a  complete  regis- 
tration of  scarlet  fever  and  diphtheria,  and  have  adopted 
rigorous  measures  of  isolation  and  disinfection,  though  in  no 
American  city  has  hospitalization  been  carried  so  far  as  it  has 
in  many  English  towns.  But  no  one  would  be  able,  by  study- 
ing mortality  rates,  to  pick  out  the  cities  which  pursue  a 
rigorous  policy  of  isolation.  I  collected  data  relating  to  the 
prevalence  of  scarlet  fever  and  diphtheria  in  American  cities 
for  the  decade  1890-1 899, ^  and  it  is  surprising  to  note  that 
the  cities  with  the  best  sanitary  administration  frequently 
have  a  comparatively  large  amount  of  scarlet  fever  and  diph- 
theria. During  the  period  mentioned,  Boston,  in  my  opinion, 
had  the  best  sanitary  administration  of  any  of  the  large  cities, 

1  Chapin,  Municipal  Sanitation,  Providence,  1901,  Table  op.  480. 


LIMITATIONS  TO   THE  VALUE  OF  ISOLATION      101 

though  New  York  stood  high.  The  death  rate  from  diph- 
theria in  both  cities  was  84  per  100,000  living,  from  scarlet 
fever  25  for  Boston,  and  33  for  New  York.  Certainly  neither 
Chicago  nor  Cincinnati  enforced  such  rigorous  measures,  yet 
the  rates  in  these  two  cities  were  72  and  71  for  diphtheria 
and  17  and  7  for  scarlet  fever.  Among  the  smaller  Mas- 
sachusetts cities  Fall  River  has  usually  had  a  rather  ineffi- 
cient health  service  and  little  hospitalization,  yet  the  death 
rate  from  diphtheria  was  21  and  from  scarlet  fever  15  per 
100,000  living,  while  in  Worcester  the  figures  were  48  and  8, 
and  this  notwithstanding  the  fact  that  in  Fall  River  the 
proportion  of  children  is  much  greater  than  in  most  Amer- 
ican cities,  and  that  the  population  is  exceptionally  ignorant 
as  measured  by  illiteracy.  Worcester  has  had  a  contagious- 
disease  hospital  since  1897,  and  has  removed  to  it  in  some 
years  as  high  as  63  per  cent  of  its  diphtheria  cases.  In  general, 
Worcester  secures  an  excellent  registration  of  cases,  and  con- 
sequent isolation.  Nevertheless  Worcester  has  recently  had, 
notwithstanding  its  increasing  hospitalization  and  good  home 
isolation,  a  severe  outbreak  of  the  disease.  It  seems  a  fair 
assumption  that  some  factor  much  more  important  than  the 
recognized  cases  of  the  disease  has  been  at  work  in  Worcester. 
If  it  were  not  so,  the  reported  cases  of  the  disease  should  not 
have  risen  from  132  in  1905  to  1178  in  1907. 

Diphtheria  Isolation  at  Home.  —  In  Providence  for  some 
years  previous  to  March,  1902,  isolation  in  diphtheria  was 
terminated  only  when  a  negative  culture  had  been  obtained 
from  the  patient.  At  that  date  a  change  was  made,  terminat- 
ing isolation  ten  days  after  the  disappearance  of  exudation. 
This  certainly  liberated  many  cases  still  infectious,  but  this 
factor  was  of  so  little  moment  that  the  disease  continued  to 
decrease  until  on  a  certain  day  in  August  the  city  was  entirely 
free  from  reported  cases,  a  condition  again  nearly  reached  in 
1907. 

Isolation  in  Institutions.  —  It  is  by  no  means  uncommon 
to  see  outbreaks  in  institutions  lasting  many  months,  al- 


102   THE  SOURCES   A.VD  MODES  OF  INFECTION 

though  every  case  is  promptly  isolated  and  all  persons  in  the 
institution  are  repeatedly  examined  by  cultures  from  throat 
and  nose.  I  have  records  of  several  such  in  Providence,  and 
most  health  officers  and  managers  of  institutions  have  been 
through  such  unpleasant  experiences.  Here  again  we  are 
forced  to  look  for  sources  other  than  the  recognizable  cases. 

At  a  school  in  Owatonna,  Minnesota/  there  had  been  more 
or  less  diphtheria  for  years  until  a  sharp  outbreak  in  1896 
caused  a  very  energetic  effort  to  be  made  to  stamp  it  out. 
Cultures  were  taken  from  everybody,  and  all  persons  in  whom 
diphtheria  bacilli  were  found  were  isolated,  at  first  in  a  com- 
mon ward,  but  later  each  person  in  a  separate  room.  Isola- 
tion was  maintained  until  three  successive  negative  cultures 
were  obtained  from  throat  and  nose,  and  efficient  disinfection 
was  practiced.  Still  the  disease  persisted  month  after  month, 
and  some  of  the  carriers,  after  release,  were  found  to  be  still 
harboring  the  bacilli.  One  boy  carried  the  bacilli  for  nineteen 
months.  The  attempt  at  the  isolation  of  carriers  was  aban- 
doned, and  several  years  later  there  was  still  more  or  less 
diphtheria  in  the  institution. 

A  still  more  notable  failure  of  the  isolation  of  diphtheria 
was  at  the  Willard  State  Hospital  for  the  insane  in  New  York.^ 
In  this  institution  practically  the  same  methods  were  adopted 
as  at  Owatonna,  but  nevertheless  the  disease  persisted  sev- 
eral years.  Patients  and  carriers  released  from  isolation  after 
several  negative  cultures  were  still  found  to  be  carriers.  If 
in  an  institution  of  this  kind,  where  the  strictest  discipline 
is  maintained,  and  where  carriers  can  be  isolated  indefinitely, 
the  most  stringent  measures  of  isolation  and  disinfection  fail 
to  stamp  out  the  disease,  what  is  to  be  expected  of  any  such 
measures  which  can  be  adopted  in  an  ordinary  community? 

An  outbreak  in  a  hospital  in  California  was  managed  in 

1  St.  Paul  M.  J.,  1900,  II,  223;  Brit.  M.  J.,  Lond.,  1898,  I,  1008;  Rep. 
St.  Bd.  Health,  Minnesota,  1897-98,  465;  Rep.  Am.  Pub.  Health  Ass., 
1899,  XXV,  546. 

*  Rep.  State  Commission  in  Lunacy,  N.  Y.,  1904,  XVI. 


LIMITATIONS   TO  THE  VALUE  OF  ISOLATION     103 

the  same  way.^  At  first  no  effect  seemed  to  be  produced, 
and  the  outbreak  lasted  from  April  to  August,  but  was  as- 
sumed to  have  been  finally  checked  by  the  same  measures 
which  failed  at  Owatonna  and  Willard.  But  as  many  out- 
breaks last  even  a  shorter  time,  though  no  attention  is  paid 
to  carriers,  it  is  uncertain  whether  the  outbreak  was  stamped 
out  or  died  out.  Sidney  Davies"  reports  that  at  the  Bostall- 
lane  School  in  Woolwich  diphtheria  prevailed  for  three  years 
notwithstanding  repeated  closures  and  bacterial  examinations 
of  the  pupils.  There  is  little  doubt  that  at  times  a  careful 
search  for  carriers  and  missed  cases  in  schools  and  institu- 
tions and  their  isolation  until  two  successive  negative  cul- 
tures from  throat  and  nose  are  obtained,  prove  successful  in 
checking  outbreaks;  there  is  no  doubt,  too,  that  outbreaks 
frequently  die  out  of  themselves;  and  it  is  shown  by  the  exam- 
ples given  above  that  it  is  at  times  impossible  by  any  degree 
of  isolation  to  stamp  out  an  outbreak.  How  to  manage  such 
institutional  epidemics  cannot  be  determined  until  the  con- 
trol of  carriers  is  more  carefully  studied  than  it  has  been. 

Isolation  a  Failure  in  Measles.  —  Measles  is  a  disease 
which  in  cities  it  seems  to  be  impossible  to  check  to  any 
appreciable  extent  by  isolation.  In  Aberdeen^  this  was  faith- 
fully tried  for  twenty  years,  1883  to  1902,  but  no  apparent 
effect  was  produced  on  the  prevalence  of  the  disease.  Similar 
failures  have  been  noted  elsewhere.  During  the  last  half  of 
this  period  in  Aberdeen,  when  there  was  far  more  accurate 
registration  and  better  control  than  before,  the  number  of 
cases  rose  to  24,254,  about  fifty  per  cent  more  than  in  the  first 
iialf  of  the  period.  A  census  of  the  children  in  certain  schools 
indicated  that  from  ninety  to  ninety-three  per  cent  of  children 
over  ten  years  of  age  had  had  the  disease.  Restrictive  meas- 
ures which  protected  only  seven  to  ten  per  cent  of  the  popu- 
lation from  attack  were  then  wisely  abandoned.     The  very 

1  Rep.  State  Bd.  of  Health,  California,  1906-08,  201. 

»  Rep.  Med.  Off.  Health,  Lend.,  1908,  36. 

'  Aberdeen,  Report  of  Med.  OflF.  of  Health,  1904,  41. 


104         THE  SOURCES  AND  MODES  OF  INFECTION 

excellent  report  of  the  medical  officer  of  health  of  Aberdeen 
discusses  the  subject  very  fully.  In  New  York  measles  was 
first  isolated  in  1896,  but  not  until  1902  were  the  regulations 
very  rigorously  enforced.  The  average  death  rate  from  1895 
to  1904  was  2.40,  and  the  highest  death  rate  since  1896  was 
reached  in  1906,  when  it  was  2.69.  There  is  no  evidence  that 
the  measures  adopted  in  New  York  have  had  any  more 
influence  on  the  prevalence  of  the  disease  than  did  isolation 
and  disinfection  in  Aberdeen.  It  seems  in  the  highest  degree 
probable  that  the  disease  prevails  because  of  the  unrecognized 
but  infectious  prodromal  stage.  No  amount  of  isolation  after 
the  disease  is  recognized  can  atone  for  the  harm  done  before 
the  diagnosis  is  made. 

Isolation  a  Failure  in  Meningitis.  —  Within  a  recent  period 
the  city  of  New  York  suffered  from  an  exceptionally  long  and 
severe  outbreak  of  cerebro-spinal  meningitis.  The  attack 
rate  was  higher  than  in  any  of  the  other  large  American  cities, 
and  the  outbreak  lasted  longer;  and  it  lasted  longer  than  it 
has  in  most  of  the  German  cities.  On  April  19,  1905,  after 
the  epidemic  had  continued  for  about  two  years,  very  strin- 
gent restrictive  measures  of  isolation  and  disinfection  were 
adopted.  The  outbreak  was  then  declining,  and  that  it  would 
afterwards  decline  still  more  was  to  have  been  expected. 
But  it  was  not  ''stamped  out,"  for  in  1907  there  were  reported 
642  deaths  and  in  1908,  351.  In  Leith '  great  efforts 
were  made  to  isolate  all  suspects  and  carriers,  and  the 
outbreak  appeared  to  be  checked,  but  in  Edinburgh  also 
it  died  out,  though  without  such  energetic  measures.  The 
experience  in  Germany  seems  to  be  that  if  in  the  beginning 
diligent  search  is  made  for  carriers,  and  strict  isolation  is 
maintained,  the  outbreak  may  sometimes  be  checked,  but 
after  the  disease  has  become  established,  and  carriers  are 
numerous,  isolation  is  of  little  avail.  These  appear  to  be 
the  views  of  Lingelsheim,  Ostermann,  Selter,  Flatten  and 
others. 

1  Ker.  Practitioner,  Lond.,  1908,  LXXX,  66. 


LIMIT ATIOXS  TO  THE  VALUE  OF  ISOLATIOX     105 

Isolation  often  a  Failure  in  Smallpox.  —  Smallpox  is  less 
likely  to  escape  detection  than  is  any  other  disease.  Yet 
epidemics  grow  in  the  face  of  the  most  rigid  isolation.  Unrec- 
ognized cases,  even  in  this  disease,  are  so  numerous  that  the 
isolation  of  the  recognized  cases  often  seems  to  be  a  complete 
failure.  The  State  Board  of  Health  of  Minnesota,  realiz- 
ing this,^  has  had  the  boldness  to  advise  that  no  attempt  be 
made  to  isolate,  and  that  entire  reliance  be  placed  on  vacci- 
nation. It  was  hoped  that  this  would  lead  to  more  complete 
vaccination.  There  has  been  no  alarming  increase  in  small- 
pox in  Minnesota,  and  IVIontana  ^  is  now  following  the  lead 
of  the  former  state. 

Why  Does  Isolation  Fail  ?  —  The  epidemiological  evidence 
is  conclusive  that  the  isolation  of  recognized  cases  of  con- 
tagious diseases  often  fails  to  check  outbreaks  which  grow 
in  spite  of  it;  that  it  does  not  stamp  out  disease,  and  that  it 
only  reduces  in  a  moderate  degree  the  prevalence  of  the 
disease.  We  are  forced  to  conclude  that  there  is  some  defect 
in  our  procedures,  or  some  other  source  of  infection  more 
important  than  the  recognized  cases.  The  error  cannot  be 
that  isolation  is  too  brief,  for  return  cases  and  recurrences 
are  not  important  factors.  It  is  not  that  isolation  is  imper- 
fect, for  isolation  in  the  hospital  is  well-nigh  complete,  and 
careful  observations  in  Providence  indicate  that  the  danger 
of  extension  outside  the  family  from  cases  at  home  is  very 
slight. 

Importance  of  Carriers  and  Missed  Cases.  —  As  has  been 
previously  stated,  two  theories  have  been  advanced  to  account 
for  the  appearance  of  untraced  cases  of  contagious  diseases: 
that  of  distant  aerial  infection,  and  that  of  the  persistence  of 
infection  on  things,  i.e.,  fomites.  In  other  chapters  of  this 
book  it  is  shown  that  both  of  these  modes  of  infection  are 
of  little  moment,  and  in  the  first  chapter  it  was  shown  to  be 

^  Resolution  adopted  July,   1906,  to  go  into  effect  January,  1908, 
Am.  J.  Pub.  HvK.,  1907,  III,  227. 
=*  Am.  J.  Pub.  Hyg.,  1909,  V,  815. 


106         THE  SOURCES  AND  MODES  OF  INFECTION 

unlikely  that  the  specific  organisms  of  our  common  diseases 
grow  outside  of  the  body.  In  the  second  chapter  it  was 
shown  that  they  may  grow  in  the  body  and  yet  produce  few 
or  no  symptoms.  It  appears,  then,  highly  probable  that  by 
far  the  most  important  factor  in  the  causation  of  the  con- 
tagious diseases  are  the  "carrier"  and  "missed"  cases. 
.  It  is  not  for  a  moment  suggested  that  the  existence  of 
carriers  explains  all  epidemiological  problems.  There  are,  for 
instance,  quite  a  number  of  contagious  diseases  which  exhibit 
a  varying  degree  of  periodicity.  We  have  as  yet  only  the 
vaguest  notions  as  to  the  causes  of  the  variations  in  the 
prevalence  of  disease,  its  seasonal  irregularities,  and  the  rise 
and  fall  of  epidemics.  There  is  no  reason  to  believe  that 
these  phenomena  depend  on  the  extra-corporal  growth  of 
pathogenic  organisms,  and  it  is  probable  that  the  seasonal 
distribution  of  such  diseases  as  smallpox  and  scarlet  fever  is 
only  in  the  most  indirect  manner  dependent  upon  tempera- 
ture, rainfall,  etc.  It  is  not  unlikely  that  the  factors  affecting 
the  extension  of  these  diseases  are  so  numerous  that  their 
prevalence  is  really  to  a  large  extent  a  matter  of  chance. 
But  whatever  the  factors  may  be,  we  must  believe  that  they 
affect  carriers  as  well  as  clinical  cases.  Why  we  have  more 
carriers  and  more  cases  at  one  time  than  another,  we  cannot 
at  present  say.  But  it  appears  to  be  in  the  highest  degree 
probable  that  in  times  of  outbreaks,  as  well  as  in  inter- 
epidemic  periods,  the  chief  factor  in  the  extension  of  the 
disease  is  the  existence  of  unrecognized  infection  in  human 
beings  or,  in  some  diseases,  in  the  lower  animals. 

Need  of  Further  Study.  —  I  would  be  the  last  person  to 
assert  that  the  views  here  set  forth  are  unassailable  and  unal- 
terable. They  doubtless  will  be  modified;  it  may  be  that 
they  are  entirely  erroneous.  What  is  needed  is  further  inves- 
tigation along  the  lines  indicated,  and  a  great  deal  of  it. 
Unfortunately  sanitary  science  is  far  from  exact.  We  have 
few  established  truths,  but  many  theories  of  greater  or  less 
probability,  on  which  to  base  our  practice.    The  probability 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION     107 

of  each  theory  must  be  carefully  weighed.  Which  is  the  most 
probable  source  of  infection,  the  cesspool  in  the  yard,  the 
fomites  that  escaped  disinfection,  the  patient  who  was  re- 
leased too  soon,  or  the  unknown  carrier  ?  The  chances  are 
greatly  in  favor  of  the  last,  and  yet  to-day  sanitary  practice 
almost  completely  ignores  the  carrier.  It  is  not  surprising 
that  many  health  officers  fail  to  appreciate  the  importance 
of  the  question  which  is  here  discussed.  It  is  remarkable, 
however,  that  bacteriologists  as  a  rule  minimize  the  danger 
to  be  apprehended  from  carriers. 

Carriers  not  to  be  Ignored.  —  It  may  be  admitted  that 
only  1  per  cent  of  the  population  are  diphtheria  carriers, 
though  as  a  matter  of  fact  it  must  often  be  fnore  than  that; 
also  that  only  15  per  cent  of  these  carry  virulent  germs,  though 
it  is  really  often  much  greater.  It  may  also  be  admitted  that 
these  bacilli  are  not  usually  so  numerous  as  in  the  sick,  though 
it  is  known  that  they  sometimes  appear  in  pure  culture;  yet 
even  admitting  all  this,  there  will  be  in  inter-epidemic  periods 
in  a  city  of  100,000  people  at  least  150  well  persons  carrying 
virulent  diphtheria  bacilli.  Why  should  the  bacteriologist 
ignore  these  150  sources  of  infection  and  insist  on  two  throat 
and  nose  negative  cultures  from  every  reported  patient  ?  Or 
why  should  he,  as  he  occasionally  does,  recommend  isolating 
the  carriers  in  the  family  but  ignore  all  other  carriers  ?  Why 
neglect  this  whole  question  of  carriers,  and  spend  endless  time 
in  devising  methods  of  liberating  formaldehyde  to  kill  the 
few  bacilli  that  may  remain  about  the  house  ?  Why  worry 
about  the  saliva  that  may  have  gotten  onto  a  book,  a  coat, 
or  the  wall  of  a  room,  and  neglect  the  reader  of  the  book, 
the  wearer  of  the  coat  and  the  dweller  in  the  room,  who  is 
probably  growing  the  germs  in  his  throat  and  nose  ?  It  is 
not  easy  to  answer  these  questions,  and  so  the  bacteriologist 
withdraws  to  his  laboratory  and  ingores  them.  But  the 
health  officer  must  answer  them  in  one  way  or  another. 

Principles  of  Diphtheria  Isolation.  —  To  confine  the  dis- 
cussion for  the  moment  to  diphtheria,  concerning  which  we 


108        THE  SOURCES  AND  MODES  OF  INFECTION 

have  more  accurate  knowledge  than  we  have  for  any  other 
disease,  there  appear  to  be  only  two  logical  positions  which 
the  health  officer  can  take  in  regard  to  its  management. 
There  is  the  possible  policy  of  non-regulation.  This  the  public 
would  certainly  not  permit,  and  I  think  with  very  good 
reason.  Or  we  can  go  to  the  other  extreme  and  attempt  to 
isolate  every  person  carrying  diphtheria  bacilli,  until  they 
disappear  from  throat  and  nose,  or  until  they  are  shown  to  be 
non-virulent.  That  is,  of  course,  entirely  impracticable  except 
in  small  isolated  communities  or  institutions,  and  it  is  often 
very  difficult,  and  sometimes  impossible  then.  In  every  large 
city  there  are  hundreds  of  carriers  who  can  never  be  detected, 
and  who  could  not  be  controlled  if  they  were.  Virulent  bacilli 
may  remain  for  months,  and  the  attempt  to  isolate  for  a  pro- 
longed period  prominent  lawyers,  business  men,  or  physi- 
cians, would  result  in  a  breakdown  of  the  whole  system. 
As  a  matter  of  fact,  such  carriers  escape  from  isolation  while 
still  infected.  If  cultures  are  taken  daily,  or  every  few  days, 
it  is  usually  not  very  long  before  the  two  negatives  required 
by  rule  are  secured  and  the  patient  is  released,  though  sub- 
sequent cultures  not  infrequently  reveal  the  bacillus.  The 
ideal  of  health  officers  has  been  to  keep  up  isolation  until 
every  spark  of  infection  has  died  out,  —  a  very  reasonable 
ideal,  until  it  was  learned  that  there  are  many  hidden  sparks 
scattered  about  the  community,  some  of  which  are  sure  sooner 
or  later  to  burst  into  flame.  As  it  is  impossible  to  attain  the 
ideal  of  stamping  out  all  infection,  and  as  it  is  certain  that 
many  infected  persons  cannot  be  restrained  at  all,  it  is  unrea- 
sonable to  require  restraint  to  the  uttermost  limit,  of  the 
recognized  cases.  It  is  often  argued  that  the  fact  that  all 
infected  persons  cannot  be  isolated,  is  no  reason  for  not  iso- 
lating all  that  can  be  found,  anymore  than  the  fact  that  many 
thieves  escape  is  no  reason  for  not  imprisoning  those  thieves 
who  are  caught.  But  there  is  no  true  parallel  here.  The 
thief  is  a  criminal,  and  his  imprisonment  is  a  punishment. 
The  bacillus  carrier  is  not  a  criminal,  and  he  is  isolated,  not 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION     109 

as  a  punishment,  but  to  protect  the  community.  If  the 
protection  secured  is  not  commensurate  with  the  hardship 
inflicted,  the  procedure  is  unjust,  and  unwise  from  a  socio- 
logical standpoint. 

A  Compromise  Necessary.  —  But  just  as  soon  as  we  depart 
from  the  orthodox  ideal,  absolute  isolation,  we  have  to  adopt 
some  sort  of  compromise,  a  compromise  which  has  no  strictly 
logical  defense.  We  are  thus  forced  to  follow  one  of  three 
policies,  —  either  do  nothing,  which  is  unwise  and  would  not 
be  permitted,  or  attempt  absolute  isolation  of  all  sources 
of  infection,  which  is  manifestly  impossible,  or  employ  a 
moderate  degree  of  restriction,  which,  though  not  strictly 
logical,  is  nevertheless  practicable,  reasonable  and  to  a  con- 
siderable degree  effective. 

Isolation  of  Real  Value.  —  While  the  most  rigorous  isola- 
tion does  not  stamp  out  diphtheria,  we  know  that  restriction 
does  some  good.  The  removal  of  a  case  to  the  hospital  is 
shown  by  statistical  evidence  to  prevent  to  some  extent  the 
development  of  secondary  cases  in  the  family.  So  too  does 
good  isolation  at  home.  The  warning  sign  on  the  house 
keeps  out  many  people,  some  of  whom  would  otherwise  cer- 
tainly^ contract  the  disease.  The  regulation  of  school  attend- 
ance prevents  some  school  outbreaks,  and  others  are  checked 
by  the  prompt  removal  of  the  infecting  child.  The  evidence 
points  to  an  appreciable  reduction  in  diphtheria  prevalence 
in  recent  times,  which  I  believe  it  is  fair  to  consider  as  due, 
in  part  at  least,  to  deliberate  separation  of  the  sick  from  the 
well  under  the  direction  of  the  sanitary  authority  or  other- 
wise. Why  more  has  not  been  accomplished  by  isolation  is 
explaincMl  by  the  facts  set  forth  in  the  preceding  chapter. 
If  because  of  the  existence  of  so  many  unrecognized  sources 
of  infection,  isolation  can  effect  only  a  limited  degree  of  pre- 
vention, could  not  substantially  as  much  be  accomplislied 
by  more  moderate  methods  than  are  usually  employed  ? 
Why  keep  the  patient  indoors  for  six  weeks  when  other  mem- 
bers of  the  family  with  infected  throats  are  going  about  ? 


110         THE  SOURCES  AND  MODES  OF  INFECTION 

Why  keep  from  work  the  wage  earners  in  an  infected  family 
when  scores  of  other  carriers  are  attending  to  their  business 
without  restraint  ? 

Typhoid  Carriers  cannot  be  Isolated.  —  The  isolation  of 
typhoid  carriers  is  no  more  possible,  just,  or  effectual  in  check- 
ing disease,  than  is  the  isolation  of  diphtheria  carriers.  As 
was  shown  in  the  preceding  chapter,  the  number  of  carriers 
and  convalescents  excreting  bacilli  is  probably  much  larger 
than  the  number  of  cases  confined  indoors.  It  seems  to  me 
useless  to  attempt  to  confine  convalescents  two  or  three 
months  after  their  recovery.  There  certainly  would  be  most 
energetic  opposition  on  the  part  of  the  public,  which  probably 
would  ultimately  be  sustained  by  the  courts.  The  health 
officer  who  attempted  to  isolate  convalescents  until  bacilli 
were  no  longer  to  be  found  in  their  urine,  would  be  in  an 
awkward  position  if  he  allowed  chronic  carriers  to  go  at  large, 
and  he  would  be  in  a  still  more  awkward  position  if  he  at- 
tempted to  isolate  all  chronic  carriers  indefinitely.  There 
are  probably  200,000  cases  of  typhoid  fever  in  the  United 
States  each  year,  and  3  per  cent  of  these  would  be  6,000. 
To  attempt  to  isolate  6,000  carriers  would  of  course  be  futile. 
Not  one-tenth  of  them  could  even  be  discovered.  To  isolate 
the  small  fraction  of  carriers  who  can  be  discovered  is  practi- 
cally useless,  and  therefore  unjust.  It  may  be,  and  probably 
is,  wise  to  regulate  the  life  of  such  carriers  as  may  be  dis- 
covered, and  at  times  to  forbid  their  engaging  in  certain 
occupations,  such  as  those  of  cook,  waitress  and  milk  dealer, 
but  to  attempt  their  isolation  under  present  conditions  seems 
to  me  most  unwise. 

Isolation  too  Rigorous.  —  I  believe  that,  on  the  whole,  iso- 
lation in  our  prevailing  contagious  diseases  is  carried  farther 
than  is  necessary;  that  less  rigorous  measures  would  accom- 
plish practically  as  much  good,  and  that  there  would  be  less 
temptation  to  conceal  cases  and  to  interpret  doubtful  symp- 
toms in  line  with  the  patient's  desires.  It  is  impossible  here 
to  lay  down  in  detail  a  scheme  for  the  proper  isolation  of 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION     .111 

contagious  diseases.  What  are  the  best  methods  of  dealing 
with  these  diseases  is  a  matter  for  free  discussion,  and  also 
for  experiment.  It  is  to  call  attention  to  the  new  facts,  and 
to  elicit  discussion  from  the  new  viewpoints,  that  these  pages 
are  written. 

Degree  of  Contagiousness.  —  Before  considering  some  of 
the  principles  which  should  guide  the  application  of  meas- 
ures of  isolation,  we  should  consider  what  are,  under  the 
ordinary  conditions  of  life,  the  chances  of  infection  from  a 
single  individual.  Until  recently  it  has  been  beheved  to  be 
very  great.  That  smallpox  hospitals  are  placed  a  mile  or 
more  from  inhabited  districts,  that  physicians  clothe  them- 
selves with  gowns  and  caps  and  rubber  boots  on  their  visits 
to  infectious  cases,  and  that  it  is  insisted  that  the  ceiling  of 
a  room  occupied  by  such  a  case  be  disinfected,  indicate  a 
belief  that  the  virus  of  the  contagious  diseases  is  exceedingly 
diffusive  and  exceedingly  virulent.  Why  such  a  belief  is  not 
well  founded  will  be  shown  in  succeeding  chapters,  and  it 
will  suffice  here  to  call  attention  to  the  fact  that  the  chance 
of  an  infected  person  transmitting  the  infection  to  another 
is  not  nearly  so  great  as  is  generally  supposed.  This  is  a 
mathematical  necessity.  We  now  know  that  the  number  of 
infected  persons  is  very  much  greater  than  was  formerly 
believed,  and  that  they  often  remain  infected  for  much  longer 
periods  than  was  suspected.  It  necessarily  follows  that  the 
danger  to  be  apprehended  from  any  one  person  at  any  one 
time  is  mucli  less  than  was  once  thought. 

Factors  Involved.  —  The  chance  of  an  infected  person  giv- 
ing rise  to  the  disease,  or  of  transmitting  the  infection  to 
others,  varies  greatly  with  the  intensity  of  the  infection,  or 
the  number  of  disease  germs  in  the  secretions  or  excre- 
tions, their  virulence,  the  volume  of  the  excretions,  the  care 
exercised,  the  occupation,  and  the  surroundings  generally. 
Conditions  in  the  home  and  in  institutions  are  usually  much 
more  favorable  than  elsewhere  for  the  transmission  of  infec- 
tion.   Yet  in  the  home  the  chance  of  such  extension  of  disease 


112         THE  SOURCES  AND  MODES  OF  INFECTION 

is  not  as  great  as  has  been  supposed.  In  Providence/  the 
chance  of  persons  contracting  diphtheria  from  another  mem- 
ber of  the  family  who  has  the  disease  is  only  about  1  in  15. 
The  chance  of  a  child  between  two  and  six  years  contract- 
ing it  is  1  in  5;  of  an  adult,  1  in  40.  The  chance  of  a  woman 
contracting  the  disease  in  the  family  is  about  three  times  as 
great  as  that  of  a  man.  For  scarlet  fever  the  figures  are 
not  very  different.  Every  one  must  have  noted  repeated 
instances  where  only  one  of  a  family  of  children  is  attacked 
by  scarlet  fever  or  diphtheria,  the  rest  of  the  family  remaining 
well,  though  isolation  may  have  been  far  from  satisfactory. 
Danger  Less  outside  Family.  —  Outside  of  the  family,  in 
school,  in  factory  and  in  ordinary  social  relations,  except  per- 
haps in  the  play  of  young  children,  the  chance  of  transmitting 
the  disease  must  be  very  much  less.  Instances  are  not  rare 
where  children,  presumably  in  the  infectious  stage  of  scarlet 
fever,  have  mingled  freely  with  others  for  many  days,  or 
perhaps  weeks,  with  little  or  no  extension  of  the  disease.  I 
have  notes  of  an  instance  where  a  boy  with  scarlet  fever  in 
the  sore-throat  stage  attended  a  Sunday-school  festival,  and 
no  other  case  developed  among  the  large  number  of  children 
present.  At  an  infant  asylum  a  child  was  sick  with  mild 
scarlet  fever  for  17  days,  mingling  freely  with  about  75  chil- 
dren, mostly  under  5  years  of  age,  and  only  3  other  cases  re- 
sulted. At  a  large  school  a  girl  returned  at  the  end  of  the 
first  week  of  an  attack  of  scarlet  fever,  and  continued  her 
attendance  for  20  days.  Only  3  or  4  cases  developed  in  that 
school.  Similar  and  even  more  marked  instances  of  appar- 
ently feeble  infectivity  are  reported  by  others.  I  have  made 
no  attempt  to  collect  such  cases,  but  I  happen  to  have  before 
me  three  reported  by  Butler."  One  child,  taken  sick  Novem- 
ber 5,  attended  school  from  November  11  to  November  19. 
Two  other  children,  attacked  December  26  and  27  respec- 
tively, attended  different  schools  up  to  January  16.     In  only 

'   Rep.  Supt.  of  Health,  Providence,  1909. 

2  Butler,  Proc.  Roy.  Soc.  Med.,  Lond.,  1908,  I,  Epidemiol.  Sec,  225. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION      113 

one  of  the  three  schools  did  even  a  single  case  occur.  I  have 
known  of  a  teacher  with  virulent  diphtheria  bacilli  in  her 
throat  from  the  first  of  January  to  the  middle  of  April,  who 
taught  in  a  kindergarten  all  that  time,  but  who  did  not  trans- 
mit the  disease  to  any  one.  Many  of  the  instances  of  typhoid 
carriers  which  have  been  referred  to,  show  that  such  persons 
may  for  long  periods  of  time  fail  to  infect  any  one,  even  though 
employed  as  cooks  or  handlers  of  milk.  I  have  known  of 
cases  of  smallpox  remaining  for  several  days  in  lodging 
houses  or  hospital  wards,  or  traveling  on  railroads,  without 
any  one  contracting  the  disease.  Failure  to  infect  maj^  be 
due  sometimes,  perhaps,  to  intermittency  in  the  excretion  of 
germs,  sometimes  to  lack  of  contact,  and  sometimes  to  lack 
of  susceptibility  on  the  part  of  the  receiver  of  the  infection. 
AVhatever  the  cause  may  be,  we  must  recognize  that  an 
infected  person  often  mingles  freely  with  the  public  without 
transmitting  the  infection  to  another. 

Carriers  less  Infective  than  the  Sick.  —  As  has  been 
stated,  it  is  not  improbable  that  the  infectivity  of  a  well  car- 
rier may  for  several  reasons  be  less  than  that  of  a  person  sick 
with  the  disease.  It  may  then  be  argued  that  the  danger 
from  carriers  has  in  the  preceding  pages  been  very  much 
exaggerated.  It  is  not  to  be  denied  that  the  probable  danger 
from  a  single  carrier  is  small.  Their  number,  however,  is 
large,  so  that  the  danger  from  all  carriers  is  large,  and  is, 
I  believe,  a  very  considerable  factor  in  the  maintenance  of 
the  contagious  diseases. 

Isolation  should  Vary.  —  In  applying  isolation  to  the 
prevention  of  disease  it  must  be  kept  in  mind  that  different 
conditions  require  different  procedures.  Thus  when  an  ordi- 
nary contagious  disease  first  appears,  after  a  considerable 
absence,  in  a  small  community,  or  in  an  institution,  very 
rigorous  measures  of  isolation  are  usually  desirable,  as  expe- 
rience has  shown  that  very  often  an  outbreak  is  thus  effec- 
tively checked  in  its  beginning. 

Isolation  in  Villages.  —  The  efficacy  of  isolation  under  such 


114         THE  SOURCES  AND  MODES  OF  INFECTION 

circumstances  is  well  illustrated  by  the  history  of  outbreaks 
of  the  common  contagious  diseases  in  the  smaller  cities,  town- 
ships and  villages  of  Michigan.  The  data  given  in  the  annual 
reports  of  the  board  of  health  of  that  state  are  of  great  epi- 
demiological interest,  and  my  discussion  of  the  subject  on 
another  occasion  is  here  given. ^ 

"  Only  those  places  are  considered  which  have  remained 
free  from  the  disease  for  at  least  sixty  days,  and  this  unfor- 
tunately is  never  true  of  a  city  of  any  considerable  size.  The 
outbreaks  reported  are  arranged  in  groups,  one  in  which  iso- 
lation and  disinfection  were  both  enforced,  one  in  which  they 
were  both  neglected,  and  one  in  which  the  reports  did  not 
state  with  sufficient  exactness  what  restrictive  measures  were 
carried  out.  The  following  is  a  summary  of  some  of  the 
tables  in  the  report : 


Number  of  Cases 
per  Outbreak. 

Number  of  Cases 
per  Outbreak. 

Restric- 
tive Meas- 
ures not 
Enforced. 

Restric- 
tive 

Meas- 
ures 
En- 

forrerl. 

Restric- 
tive Meas- 
ures not 

Enforced. 

Restric- 
tive 
Measures 
Enforced. 

Typhoid  fever,  10  years .  . 

Diphtheria,  14  years 

Scarlet  fever,  14  years .... 

Measles,  11  years 

Smallpox        

5.82 

11.12 
11.95 
48.30 

3.13 
2.11 
2.32 
3.03 

1900 

6.72 

4.85 

10.43 

27.60 

32.00 

2.22 
1.71 
2.53 
4.67 
3.80 

Isolation  Efifective.  —  "  Several  things  are  to  be  noted  in 
connection  with  these  figures.  In  the  first  place,  isolation 
and  disinfection  accomplish  very  much  in  preventing  the 
extension  of  all  these  diseases.  The  number  of  facts  is  sd 
great,  the  outbreaks  of  each  disease  running  into  the  hun- 
dreds, and  the  difference  between  good  and  bad  sanitation  is 
so  manifest  in  each  one  of  the  years  for  each  one  of  the 

'  J.  Mass.  Ass.  Bds.  Health,  Best.,  1904,  XIV,  226. 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION      115 

diseases,  that  the  success  achieved  must  be  a  very  real  one. 
It  appears  certain  that  isolation  and  disinfection  as  practiced 
in  the  smaller  communities  of  Michigan  reduce  the  cases  of 
contagious  disease  in  round  numbers  from  forty-five  to  ninety- 
five  per  cent.  In  scarlet  fever,  diphtheria,  measles  and  small- 
pox, isolation  appears  from  the  reports,  as  one  would  expect, 
to  have  very  much  more  restrictive  effect  than  disinfection. 

"As  will  be  shown  later,  disinfection  probably  has  little 
influence  in  restricting  contagious  diseases,  but  in  view  of 
existing  ideas  and  practices  it  is  probable  that  isolation  and 
disinfection  were  not  so  distinctly  separable  as  is  indicated  by 
the  reports  of  the  local  health  officers.  One  of  the  things 
which  appeared  most  remarkable  to  the  writer  in  these  re- 
ports is  the  apparently  great  restriction  of  measles.  It  has 
certainly  been  the  experience  in  all  our  larger  cities  that 
restrictive  measures,  no  matter  how  energetic,  have  had  very 
little  effect  in  reducing  the  mortality  from  this  disease.  But 
in  the  smaller  communities  in  Michigan  it  appears  that  where 
isolation  and  disinfection  are  well  carried  out  there  is  nearly 
ninety-four  per  cent  less  cases  per  outbreak  than  where  pre- 
cautions are  neglected. 

Cause  of  Success.  —  "  But  if  one  examines  the  original 
returns  of  the  health  officers  it  appears  plain  why  such  good 
results  are  obtained.  If  the  first  case  of  the  disease  coming 
to  a  community  is  early  recognized  and  isolated  the  chances 
are  good  that  the  outbreak  will  be  at  once  checked.  The 
chances  that  such  a  ca.se  will  be  so  recognized  in  a  village  are 
very  much  greater  than  in  a  city.  If,  however,  the  outbreak 
is  not  checked  at  its  very  outset,  the  chances  are,  even  in  the 
country,  that  its  extension  will  be  very  considerable.  As  a 
matter  of  fact,  a  great  many  of  the  first  cases  coming  to  small 
communities  are  promptly  recognized  and  isolated,  and  as  a 
result  an  outbreak  is  prevented.  It  is  because  outbreaks  are 
in  rural  communities  so  often  nipped  in  the  bud  that  the 
api)licati()n  of  restrictive  measures  in  such  communities  makes 
such  a  good  showing.    What  is  true  of  measles  is  true  also 


116         THE  SOURCES  AND  MODES  OF  INFECTION 

of  other  diseases,  particularly  of  scarlet  fever  and  diphtheria. 
It  is  success  in  applying  restrictive  measures  to  the  first  case 
that  is  the  principal  cause  of  the  apparent  efficiency  of  these 
methods.  If  every  appearance  of  contagious  disease  in  these 
rural  communities  had  gained  some  headway  before  restric- 
tive measures  were  applied,  the  showing  would  not  be  nearly 
so  favorable.  In  fact,  in  the  large  cities  in  Michigan,  where 
these  diseases  are  always  epidemic,  restrictive  measures,  even 
of  a  very  rigorous  type,  have  not  enabled  the  health  officers 
to  '  stamp  them  out.'  Thus  in  Detroit  it  was  the  custom 
for  many  years  to  'quarantine'  absolutely  every  house 
where  there  was  scarlet  fever  or  diphtheria.  No  one  was 
allowed  to  go  out,  and  the  inspectors  visited  the  house  twice 
a  day  and  furnished  provisions  for  the  poor  at  an  expense 
of  thousands  of  dollars  annually.  Yet  these  diseases  were  no 
more  'stamped  out'  in  Detroit  than  they  have  been  in 
Chicago  or  other  cities  where  milder  methods  have  prevailed." 

Isolation  in  Common  Diseases.  —  When  measles,  diph- 
theria or  scarlet  fever  appears  in  a  town  or  institution  which 
has  for  some  time  been  free  from  the  disease,  the  patient  ought 
to  be  isolated  until  it  is  as  certain  as  medical  science  can 
determine  that  he  is  free  from  infection.  At  least  this  should 
be  attempted.  If  it  should  happen,  as  it  sometimes  does, 
that  the  diphtheria  patient  retains  virulent  bacilli  for  many 
months,  or  that  the  scarlet-fever  patient  has  a  discharging 
ear  for  a  similar  period,  isolation  will  probably  have  to  be 
abandoned.  But  isolation  is  worth  trying,  for  in  the  majority 
of  instances  safety  is  secured  in  a  few  weeks.  Contacts  also 
should  be  carefully  examined  and  isolated,  or  otherwise  re- 
stricted as  to  their  relations  with  the  community.  If  after 
a  reasonable  time  the  disease  is  "  stamped  out  "  the  health 
officer  is  to  be  congratulated.  If  it  is  not  stamped  out  he 
may  well  temper  the  rigor  of  his  restrictive  measures. 

When  a  rare  disease,  as  plague,  leprosy,  or  cholera,  appears 
in  Europe  or  North  America,  equally  stringent  measures 
should  be  employed.     At  present  smallpox  belongs  rather 


LIMITATIOXS  TO   THE  VALUE  OF  ISOLATIOX       117 

to  this  class  of  rare  diseases,  and  strict  isolation  of  the  first 
case  and  careful  examination  and  supervision  of  contacts  is 
desirable  and  useful. 

Many  Carriers  make  Isolation  Useless.  —  The  effective- 
ness of  isolation,  and  the  consequent  reason  for  its  practice, 
varies  inversely  as  the  number  of  carriers  and  missed  cases. 
With  the  enormous  number  of  carriers  of  pneumococci,  it  is 
entirely  useless  to  enforce  isolation  of  cases  of  pneumonia. 
Influenza  belongs  to  the  same  class  as  pneumonia,  in  which 
compulsory  isolation  is  useless.  It  is  probable  also  that  noth- 
ing which  the  health  officer  can  do  in  the  way  of  isolation 
will  have  any  effect  on  the  extent  of  outbreaks  of  cerebro- 
spinal meningitis.  The  enforced  isolation  of  typhoid  fever, 
owing  to  the  number  of  carriers,  will  usually  prove  of  little 
value.  While  it  is  probable  that  there  are  few  carriers  of 
measles,  yet  the  long  prodromal  but  extremely  infectious 
stage  renders  ineffectual  measures  of  restriction.  If  isolation 
of  measles  is  attempted,  little  can  be  hoped  for  other  than  a 
slight  postponement  of  the  age  of  attack,  and  no  measures 
should  be  adopted  which  inflict  any  great  hardship.  No  one 
advocates  the  isolation,  in  the  ordinary  meaning  of  the  term, 
of  pulmonary  tuberculosis.  It  is  not  attempted  in  this 
disease  simpl}'  because  infected  persons  are  so  numerous  that 
it  is  impossible.  If  tuberculosis  were  as  rare  as  leprosy,  strict 
isolation  would  be,  and  should  be,  demanded.  On  the  other 
hand,  there  are  so  few  carriers  of  smallpox  that,  even  Avith 
the  mild  type  of  the  disease  prevailing,  strict  isolation  is  often 
advisable. 

To  discover  the  proportion  of  carriers  to  recognized  cases, 
for  each  disease,  is  a  matter  of  the  greatest  practical  impor- 
tance. We  must  have  a  fairly  clear  idea  of  how  many  un- 
recognized human  foci  of  infection  there  are  before  we  can 
determine  upon  what  methods  of  isolation,  if  any,  are  likely 
to  prove  effective.  Yet  the  investigation  of  carriers  has 
received  comparatively  little  attention  at  the  hands  of 
bacteriologists. 


118         THE  SOURCES  AND  MODES  OF  INFECTION 

Value  of  Hospitals.  —  Hospitals  are  useful  for  protecting 
the  family,  for  checking  outbreaks  in  institutions,  for  receiv- 
ing cases  from  lodging  houses  and  hotels,  for  furnishing  better 
medical  service,  and  for  relieving  the  overworked  housewife 
in  the  families  of  the  poor.  It  is  an  unnecessary  expense 
to  provide  hospital  accommodations  for  all  cases  of  scarlet 
fever  and  diphtheria,  or  for  ninety  per  cent  or  even  eighty 
per  cent.  That  half  or  two-thirds  of  the  cases  of  these 
diseases  can,  for  all  practical  purposes,  be  equally  well  cared 
for  at  home,  is  not  unlikely. 

Home  Isolation.  —  In  home  isolation  of  scarlet  fever,  diph- 
theria and  measles,  the  patient  should,  for  the  benefit  of  the 
public,  be  kept  in  the  house.  It  does  not  seem  reasonable  to 
prolong  isolation  until  all  possible  chance  of  infection  has 
ceased.  Exactly  what  the  period  should  be  in  each  disease 
should  now  be  a  topic  for  renewed  discussion. 

Isolation  in  Providence.  —  In  Providence  at  present  the 
period  of  isolation  for  scarlet  fever  is  four  weeks  from  the 
beginning  of  the  case.  Up  to  1902  the  period  was  five  weeks. 
Since  the  reduction  in  the  period  of  isolation,  the  attack  rate 
has  been  about  33  per  100,000  living,  although  one  of  our 
largest  epidemic  waves  occurred  during  this  period,  and  regis- 
tration is  certainly  far  better  than  formerly.  From  1884  to 
1901  the  attack  rate  was  about  34  per  100,000.  In  diph- 
theria, isolation  is  maintained  for  ten  days  after  the  disap- 
pearance of  the  membrane.  The  decrease  in  the  prevalence 
of  the  disease  which  followed  the  adoption  of  less  rigorous 
isolation  has  been  previously  alluded  to. 

Family.  —  When  the  attempt  is  made  to  isolate  the  patient 
in  the  family  from  the  family,  in  order  to  protect  other  mem- 
bers, the  duration  of  isolation  may  well  be  left  to  the  dis- 
cretion of  the  family.  It  is  the  duty  of  the  health  officer 
to  explain  that  the  longer  the  separation  of  sick  from  well 
is  maintained,  the  more  likely  it  is  to  be  effective.  In  scarlet 
fever  there  is  no  means  of  determining  when  the  patient  is 
free  from  infection.     I  am  in  the  habit  of  recommending- 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION       119 

separation  from  the  family  for  six  weeks,  perhaps  a  somewhat 
shorter  time  if  the  case  is  a  mild  one,  and  longer  if  there  is 
aural  or  nasal  discharge.  In  Providence,  scarlet-fever  cases 
are  usually  sent  home  from  the  hospital  in  four  or  five  weeks, 
if  free  from  nose  and  ear  discharge.  No  regard  need  be  paid 
to  desquamation,  as  the  experience  of  English  hospitals  has 
shown  that  no  danger  is  to  be  feared  from  that  source.^  It 
is  absurd  to  isolate  with  strictness  a  diphtheria  patient  from 
the  rest  of  the  family  unless  cultures  have  shown  that  the 
rest  of  the  family  are  free  from  the  bacilli.  If  such  home  iso- 
lation is  to  be  undertaken  at  all,  it  should  be  continued,  if 
possible,  until  two  or  three  successive  negative  cultures  have 
been  obtained. 

Hospital.  —  Diphtheria  cases  in  Providence  are  usually  in 
the  hospital  until  two,  three  or  four  successive  negative  cul- 
tures from  the  throat  have  been  secured,  the  greater  precau- 
tion being  taken  when  the  child  is  to  return  to  an  institution. 
Sometimes  the  patient  is  sent  out  while  still  harboring  bacilli. 
The  duration  of  isolation  of  the  living  cases  is  19.65  days, 
and  the  percentage  of  return  cases  has  been  1.9.  In  London  ^ 
the  period  of  detention  of  6866  cases  was  57.5  days,  and  the 
percentage  of  return  cases  was  1.2,  about  0.5  per  cent  less 
than  in  Providence,  although  the  period  of  detention  was 
almost  three  times  as  long.  The  duration  of  stay  in  the  Provi- 
dence hospital  for  scarlet  fever,  surviving  cases,  is  45.67  days, 
and  the  percentage  of  return  cases  is  3.4.  In  the  London 
hospitals  the  period  of  detention  is  64.9  days,^  and  the  per- 
centage of  return  cases,  1902-04,  was  3.22. 

>  Metropolitiin  Asylums  Board  Report  on  Return  Cases  of  Scarlet 
Fever  and  Diphtheria,  1902-04,  6.  See  also  my  discussion  of  this  subject 
in  FiskeFund  Essay LII,pubn.shed  by  R.I.  Medical  Society, Providence, 
1909. 

2  Metropolitan  Asylums  Board  Report  on  Return  Cases  of  Scarlet 
Fever  and  Diphtheria,  1901-02,  59,  62. 

'  Metropohtan  Asylums  Board  Report  on  Return  Cases  of  Scarlet 
Fever  and  Diphtheria,  1902-04,  5,  23. 


120         THE  SOURCES  AND  MODES  OF  INFECTION 

School.  —  School  children  in  infected  families  should  be 
excluded  from  school  for  a  liberal  period,  for  this  works  little 
hardship,  and  the  state  should  make  special  effort  to  keep 
its  schools  free  from  disease.  Yet  school  exclusion  may  be, 
and  often  is,  carried  to  excess.  In  Providence  children  living 
in  a  family  where  there  is  scarlet  fever  are  excluded  from 
school  for  four  weeks  from  the  beginning  of  the  last  ease. 
In  all  except  the  poorer  class  of  houses  children  living  in 
other  families  in  the  house  are  permitted  to  attend  school. 
In  diphtheria,  children  in  the  infected  family  are  not  allowed 
in  school  for  four  weeks,  provided  that  if  all  the  school  chil- 
dren in  the  family  yield  two  throat  and  nose  negative  cultures, 
they  may  attend  school  after  the  warning  sign  has  been 
removed  (which  is  ten  days  after  the  disappearance  of  the 
exudation).  Children  in  other  families  in  the  better  class  of 
houses  are  admitted  to  school  if  one  negative  culture  is  ob- 
tained from  throat  and  nose.  After  the  expiration  of  a  month, 
all  children  in  families  where  there  has  been  diphtheria  are 
usually  admitted  to  school  whether  or  not  they  are  carrying 
morphologically  typical  bacilli,  and  of  course  quite  a  number 
do  go  to  school  while  infected.  Doubtless  these  carriers  may 
at  times  infect  others  in  school,  but  even  if  two  negative  cul- 
tures were  required  before  readmission,  some  children  would 
probably  still  prove  infectious.  Absolute  security  is  impos- 
sible, and  the  rule  should  be  so  framed  as  to  accomplish  a 
maximum  amount  of  good  with  a  minimum  amount  of  an- 
noyance. 

Wage  Earners.  —  There  is  little  reason  for  excluding  wage 
earners  from  their  work  except  in  a  few  occupations.  Most 
of  the  carriers  we  cannot  restrain,  and  therefore  why  penalize 
those  who  have  the  additional  misfortune  of  sickness  in  their 
families  ? 

The  most  dangerous  carriers  are  those  who  handle  milk; 
hence  milk  producers  and  dealers  living  in  infected  families 
should  be  excluded  from  work.  Judging  from  the  number 
of  reported  outbreaks,  the  danger  is  probably  greater  for 


LIMITATIONS  TO  THE  VALUE  OF  ISOLATION       121 

typhoid  fever  than  for  any  other  disease.  It  is  probably  wise 
to  regulate  the  occupation  of  all  typhoid  contacts  who 
handle  any  kind  of  food  that  is  eaten  raw.  Perhaps  the  same 
should  be  done  with  diphtheria  contacts.  Teachers  and 
nurses  may  very  properly  be  prevented  from  following  their 
usual  vocations  if  they  live  in  infected  families.  It  has  been 
my  custom  also  to  exclude  from  work  car  conductors,  post- 
men, barbers  and  department-store  clerks.  I  doubt,  however, 
whether  this  is  always  advisable.  I  am  very  sure  that 
laborers,  mill  operatives  and  office  clerks  need  not,  under 
ordinary  circumstances,  be  kept  from  their  business. 

Summary. — As  regards  the  employment  of  isolation  for 
the  prevention  of  the  spread  of  infectious  disease  we  may 
fairly  conclude: 

1.  The  danger  to  be  apprehended  from  a  single  infected 
person  is  much  less  than  has  been  supposed. 

2.  Isolation  is  of  far  less  value  than  was  believed  a  few 
years  ago. 

3.  The  fewer  the  infected  persons  in  any  community  or 
institution  the  more  likely  is  isolation  to  be  successful.  Iso- 
lation in  an  extensive  outbreak  rarely  accomplishes  much. 

4.  The  effectiveness  of  isolation  varies  inversely  as  the 
number  of  missed  cases  and  carriers. 

5.  Hospitalization  in  such  diseases  as  scarlet  fever  and 
diphtheria  cannot  be  expected  to  exterminate  them,  and  the 
majority  of  patients  can  be  as  well  cared  for  in  their  homes. 

6.  In  diphtheria,  scarlet  fever  and  measles  there  is  rarely, 
and  only  in  certain  occupations,  any  necessity  for  interfering 
with  the  freedom  of  the  wage  earners  of  the  family. 

7.  The  isolation  of  school  children  should  be  more  strict 
than  that  of  adults,  for  less  hardship  results,  and  there  is 
more  danger  in  the  mingling  of  children  than  in  the  inter- 
course of  adults. 


CHAPTER  IV. 

INFECTION  -BY  CONTACT. 

Most  Obvious  Mode.  —  Contact  infection  is  the  most 
obvious  mode  of  transmission  of  the  infectious  diseases.  For 
the  sick  to  touch  the  well,  and  thus  infect  them,  seems  to  be 
the  most  natural  way  of  accounting  for  the  spread  of  these 
diseases.  If  contact  infection  can  explain  epidemiological 
phenomena,  there  is  no  occasion  for  assuming  the  growth  of 
pathogenic  germs  outside  of  the  body,  or  of  infection  by  fo- 
mites  or  infection  by  air,  or  any  other  similar  theory,  and 
no  such  theory  should  be  adopted  as  a  working  hypothesis 
unless  pretty  strong  evidence  can  be  brought  to  its  support. 

Venereal  Diseases.  —  Gonorrhea  and  syphilis  are  univer- 
sally believed  to  be  transmitted  exclusively  by  contact,  and 
almost  invariably  by  a  special  kind  of  contact.  This  idea  is 
so  firmly  fixed  in  the  minds  of  medical  men  and  the  laity, 
that  no  matter  how  many  cases  occur  which  it  is  impossible 
to  trace  to  their  source,  no  one  ever  suggests  that  these 
diseases  are  air-borne,  or  that  their  germs  maintain  a  sapro- 
phytic life.  No  matter  how  much  the  patient  may  protest, 
it  will  still  be  held  that  the  infection  is  due  to  contact,  and 
in  the  vast  majority  of  cases  to  contact  involved  in  the  sexual 
act.  Gonorrhea,  particularly,  is  believed  to  be  almost  never 
transmitted  except  by  the  most  direct  contact;  yet  there  is 
at  times  as  much  reason  for  assuming  that  the  gonococcus 
is  air-borne,  or  clings  to  the  walls  of  rooms  and  thence  infects 
their  occupants,  as  there  is  to  assume  the  same  for  scarlet 
fever.  Yet  so  firmly  are  we  held  by  tradition  that  if  any  of 
us  should  suggest  such  an  origin  for  gonorrhea  it  would  pro- 
voke onl}^  a  smile,  while  such  sources  of  scarlet  fever  are 

accepted  as  well  established. 

122 


INFECTIOX  BY  CONTACT  123 

Gonorrhea  in  Babies'  Hospital.  —  The  spread  of  gonococ- 
cus  infection  in  institutions  for  children  is  very  suggestive  of 
the  ways  in  which  other  infections  are  transmitted. 

A  very  interesting  account  of  institutional  infection  is  given 
by  Holt.i  At  the  Babies'  Hospital  in  New  York,  from  1894 
to  1898  inclusive,  64  cases  of  gonococcus  vaginitis  were  admit- 
ted, and  16  cases  developed  in  the  hospital.  In  the  summer 
of  1899,  three  children  suffering  from  gonococcus  vaginitis 
were  inadvertently  admitted  to  the  country  branch  of  the 
hospital,  and  though  the  danger  was  realized,  and  every  effort 
was  made  to  prevent  the  extension  of  the  disease,  by  pro- 
viding separate  nurses  for  the  infected  cases,  by  washing  the 
napkins  separately,  and  boiling  and  disinfecting  them,  never- 
theless 15  girls  contracted  vaginitis.  In  1901  similar  trouble 
was  experienced,  and  notwithstanding  the  most  vigorous 
measures  of  isolation  and  napkin  disinfection,  22  cases  devel- 
oped in  the  one  cottage  to  which  the  three  original  cases 
were  admitted.  The  physicians  were  inclined  to  look  upon 
general  house  infection  as  the  only  explanation  of  the  origin 
of  the  cases.  In  November,  1902,  a  new  hospital  building 
was  occupied  for  the  first  time,  and  it  was  hoped  that  it  could 
be  kept  free  from  the  disease,  but  5  cases  were  unwittingly 
admitted  during  the  first  six  months,  and  29  cases  of  vagi- 
nitis and  8  of  gonococcus  arthritis  developed  in  the  institu- 
tion. During  the  year,  13  cases  were  admitted,  and  66  were 
contracted  in  the  hospital.  Although  the  infected  cases  were 
all  strictly  isolated,  on  two  occasions  a  child,  even  in  another 
part  of  the  hospital,  developed  the  disease.  For  a  time 
napkins  were  discarded  and  pads  used,  which  could  be 
burned;  separate  thermometers,  baths  and  supplies  were 
required  for  each  child;  wash  cloths  were  burned,  and  tub 
baths  forbidden.  Bed  clothing  was  disinfected  with  the 
greatest  care.  Inhere  was  thought  to  be  absolutely  no 
opportunity  for  direct  contact  between  child  and  child. 
When  diphtheria  or  scarlet  fever  persists  in  an  institution  in 

1  Holt,  N.  York  M.  J.  [etcl,  1905,  LXXXI,  521. 


124         THE  SOURCES  AND  MODES  OF  INFECTION 

such  a  manner,  it  is  at  once  attributed  to  persistent  infection 
of  the  building  itself,  and  it  is  suggested  by  Holt  as  a  pos- 
sibility in  this  instance  also. 

Carried  by  Nurses.  —  But  the  gonococcus  is  an  excep- 
tionally frail  organism,  and  it  is  impossible  to  believe  that 
persistent  infection  of  a  building  or  its  contents  can  occur. 
Actually,  in  the  Babies'  Hospital,  it  v/as  found  that  the  nurse 
was  the  carrier  of  the  germs  from  child  to  child,  and  the  two 
cases  which  developed  in  distant  wards,  and  which  were  sup- 
posed to  be  perfectly  isolated  and  under  the  care  of  different 
nurses,  were  attended  by  the  same  night  nurse  who  looked 
after  the  infected  cases.  Finally,  when  the  strictest  disin- 
fection had  failed  to  check  the  disease,  it  was  at  last  con- 
trolled by  requiring  that  the  nurses  should  practice  a  strict 
medical  asepsis,  and  disinfect  the  hands  in  every  instance 
immediately  after  bathing  or  changing  the  napkins  of  each 
child.  Here  was  a  disease  which  continued  to  spread  after 
the  erratic  and  persistent  manner  of  scarlet  fever  and  diph- 
theria, and  which  was  shown  to  depend  exclusively  upon  con- 
tact infection.  Air-borne  infection  and  fomites  infection  can 
have  no  part  in  institutional  gonococcus  infections,  for  the 
gonococcus  dies  so  quickly  that  such  modes  of  transfer- 
ence are  impossible.  Yet  this  infection  is  most  persistent 
and  troublesome  in  many  institutions  for  the  care  of  young 
children. 

Contact  not  always  Direct.  —  Gonorrheal  infection  is  not 
only  quite  common  in  institutions,  but  it  is  often  found  in 
infants  and  young  children  in  their  homes.  It  is  believed 
to  result  usually  from  the  child  sleeping  with  its  parents,  or 
to  direct  contact  with  the  hands  of  the  mother  while  washing 
or  dressing  the  child.  I  have  also  known  of  cases  of  the  direct 
transfer  of  the  disease  on  instruments  in  a  physician's  office. 

It  has  thus  been  necessary  to  modify  our  conception  of 
the  mode  of  transmission  of  gonorrhea,  and  although  it  is 
still  conceived  of  as  due  exclusively  to  contact  infection,  it 
is  now  recognized  that  the  contact  need  not  always  be  direct 


INFECTION  BY  CONTACT  125 

between  the  sick  and  the  well,  but  some  infected  person  or 
thing  may  act  as  intermediary.  Yet  from  what  is  known  of 
the  weak  resistance  of  the  gonococcus,  the  interval  of  time 
must  be  brief.  The  term  contact  infection  as  now  employed 
means  just  that  kind  of  transference  of  rather  fresh  infecting 
material  from  one  to  another.  It  does  not  necessarily  imply 
actual  contact  between  sick  and  well,  but  it  does  imply  that 
there  are  no  long  intervals  of  time  in  which  the  infective 
materials  may  become  dry  and  inert.  The  transfer  of  gonor- 
rheal pus  from  child  to  child  on  a  syringe,  or  on  the  fingers 
of  the  nurse,  are  examples  of  contact  infection.  If  the  pillow 
used  by  an  infected  child  were  put  away  for  a  week  or  two, 
and  when  brought  out  caused  ophthalmia  in  the  infant  who 
used  it,  it  Avould  be  an  example  of  fomites  infection.  The 
distinction  between  the  two  types  of  disease  transference, 
though  not  sharply  or  accurately  defined,  is  a  reasonable  and 
practical  one.  Thus  every  one  admits  that  gonorrhea  is  fre- 
quently transferred  by  indirect  contact  infection,  as  it  may 
be  called,  but  it  is  never  suggested  that  this  disease  is  spread 
by  fomites. 

S3rphilis  spread  solely  by  Contact.  —  While  it  appears  to 
be  pretty  well  determined  that  Treponema  pallida  is  the 
cause  of  syphilis,  we  have  as  yet  no  data  as  to  the  cultivation 
of  this  organism  or  its  persistence  outside  of  the  body.  Its 
cultivation  outside  the  body  certainly  is  not  easy,  and  it  may 
be  suspected  that  its  life  is  short;  but  it  is  not  impossible 
that  the  virus  may  retain  its  virulence  for  some  days  or  weeks, 
as  does  that  of  rabies,  variola  and  vaccinia.  At  present  we 
have  to  rely  solely  on  clinical  evidence  as  to  these  points,  and 
the  universal  opinion  of  this  much  studied  disease  is  that 
the  virus  develops  only  in  human  beings  (and  some  of  the 
apes),  that  it  is  not  very  persistent,  and  that  it  is  trans- 
mitted solely  by  contact.  No  one  has  ever  suggested  that 
syphilis  is  an  air-borne  disease  in  the  ordinary  sense,  though 
one  or  two  cases  of  droplet  infection  have  been  reported.' 
»  Buckley,  Syphilis  in  the  Innocent,  N.  Y.,  1894,  176. 


126         THE  SOURCES  AXD  MODES  OF  INFECTION 

No  matter  how  obscure  may  be  the  origin  of  cases,  no  one 
would  attribute  them  to  aerial  infection,  or  to  dwelling  in  an 
infected  house.  Infection  during  the  sexual  act  is  undoubt- 
edly the  cause  of  by  far  the  larger  proportion  of  the  cases  of 
this  disease,  yet  in  the  aggregate  a  great  number  of  cases  are 
caused  in  other  ways. 

Non-sexual  Contact.  —  Buckley  in  the  work  just  quoted 
shows  that  probably  ten  per  cent  of  the  initial  lesions  are 
extragenital.  Exceedingly  infectious  lesions  are  at  a  certain 
stage  of  this  disease  frequently  found  in  the  mouth,  so  that 
it  is  not  surprising  that  the  second  most  important  source 
of  the  disease  is  another  form  of  direct  contact,  namely  kiss- 
ing. Other  forms  of  direct  contact  are  often  reported,  as 
nursing,  and  sucking  wounds.  That  mediate  contact  by 
means  of  all  sorts  of  articles  infected  with  saliva,  or  more  rarely 
other  secretions,  is  common,  is  now  well  known,  and  Buck- 
ley has  collected  many  hundreds  of  instances  of  such  modes 
of  transference.  Among  various  bearers  of  infection  reported 
by  Buckley  may  be  mentioned  cups,  glasses,  spoons  and  other 
eating-utensils,  pipes,  toilet  articles,  underclothing,  bathing 
suits,  handkerchiefs,  bedding,  pins,  string,  wind  instruments 
of  all  kinds,  glass  blowers' tubes,  pencils,  coins,  nursing-bottles, 
sponges,  syringes,  surgeons'  instruments,  dentists'  tools  and 
barbers'  utensils.  But  the  possible  ways  in  which  the  disease 
can  be  spread  by  indirect  contact  are  almost  infinite,  and  the 
larger  part  of  Buckley's  book  is  occupied  by  their  enumeration. 
A  perusal  of  these  reports  is  extremely  interesting,  for  while  it 
is  not  claimed  that  every  case  narrated  was  caused  in  the  man- 
ner assumed,  yet  it  is  evident  that  all  such  modes  of  trans- 
mission are  possible,  and  one  is  greatly  impressed  by  the  vast 
number  of  ways  in  which  fresh  secretions  may  be  passed  from 
one  to  another.  While  the  time  during  which  the  various 
articles  retained  their  infection  is  unknown,  or  at  least  is  not 
given  in  the  reports  of  cases,  it  is  apparent  that  almost  none 
of  the  instances  of  mediate  contact  were  the  result  of  long  per- 
sistent  infection.     Fomites  infection  is  not  an  important. 


INFECTIOX   BY  COXTACT  127 

factor  in  the  spread  of  sj'philis.  Buckley^  says  that  the 
danger  from  soiled  clothing,  rags,  or  second-hand  garments 
"  is  infinitely  less  than  is  commonly  supposed,  and  relatively 
few  instances  have  been  recorded,  and  none  of  these  are  very 
clear  or  satisfactory."  In  the  few  instances  which  he  gives, 
the  infective  material  might  well  have  been  very  fresh. 

Typhoid  Fever  by  Contact.  —  Of  late  years  a  great  deal 
has  been  written  about  the  transmission  of  typhoid  fever  by 
contact  from  case  to  case,  and  this  mode  of  infection  appears 
to  have  attained  greater  prominence  in  connection  with  this 
than  with  any  other  of  the  common  infectious  diseases.  My 
attention  was  first  drawn  to  the  importance  of  contact  infec- 
tion in  typhoid  fever  by  the  vivid  description  given  by  Sedg- 
wick of  an  outbreak  which  he  investigated  in  1892  in 
Bondville, Massachusetts.  Hesaysr  "Children abound; and, 
as  there  are  no  fences,  and  because  it  is  the  custom,  they  mingle 
freel}',  playing  together  and  passing  from  house  to  house. 
The  families  are  of  that  grade  in  which  food  always  stands 
upon  the  table ;  meals  are  irregular  except  for  those  who  must 
obey  the  factory  bell.  The  children  play  awhile,  then  visit 
the  privies,  and  with  unwashed  hands  finger  the  food  upon 
the  table.  Then  they  eat  awhile  and  return  to  play.  Or, 
changing  the  order  of  things,  they  play  in  the  dirt  and  eat 
and  run  to  the  privy,  then  eat,  play,  and  eat  again,  and  this 
in  various  houses  and  in  various  privies.  For  them,  so  long 
as  they  are  friendly,  all  things  are  common,  —  dirt,  dinners 
and  privies;  and,  to  illustrate  exactly  how  secondary  infection 
may  go  on,  I  may  describe  in  detail  one  case  which  I  personally 
witnessed.  A  whole  family  (of  six  or  more)  was  in  one  room. 
Four  of  them  had  the  '  fever.'  Two  of  these  were  children 
in  the  prodromal  stage.  A  table  stood  by  the  window  covered 
with  food,  prominent  among  which  was  a  big  piece  of  cake. 
It  was  early  September,  and  a  very  warm  day;  but  every 
window  was  shut  and  the  odor  sickening.    Flies  innumerable 

'  Burkloy,  Syphilis  in  tho  Innoront,  New  York,  1894,  156. 
2  Sedgwick,  Rep.  lid.  Health  Mass.,  Host.,  1892,  736. 


128         THE  SOURCES  AND  MODES  OF  INFECTION 

buzzed  about,  resting,  now  on  the  sick  people,  now  on  the 
food.  A  kind-hearted  neighbor  was  tending  the  baby.  By 
and  by  one  of  the  children  having  the  fever  withdrew  to  the 
privy,  probably  suffering  with  diarrhea,  but  soon  returning, 
slouched  over  to  the  food,  drove  away  some  of  the  flies,  and 
fingered  the  cake  listlessly,  finally  breaking  off  a  piece,  but 
not  eating  it.  Stirred  by  this  example,  another  child  slid 
from  his  seat  in  a  half-stupid  way,  moved  to  the  table,  and, 
taking  the  same  cake  in  both  hands,  bit  off  a  piece  and  swal- 
lowed it.  The  first  boy  had  not  washed  his  hands,  and  if 
the  second  boy  suffered  from  secondary  infection,  I  could  not 
wonder  at  it. 

"This  was  one  case;  but  I  have  seen  so  often  the  table  of 
food  standing  hours  long  in  the  kitchen,  and  serving  as  one 
station  in  the  dirty  round  of  lives  like  these,  that  it  is  easy 
for  me  to  understand  how  dirt,  diarrhea  and  dinner  too  often 
get  sadly  confused.  The  privies  had  been  obviously  in  bad 
condition,  and,  from  some,  filthy  streams  ran  down  between 
them  and  the  houses.  In  and  around  these  streams  the  chil- 
dren played.  Given  any  original  imported  case,  the  infection 
might  easily  have  reached  these  trickling  streams.  Children's 
fingers  might  thence  carry  the  germs  to  the  food,  and  thus 
the  journey  of  the  germs  from  one  living  intestine  to  another 
be  completed.  Or,  again,  given  in  such  a  community  an 
imported  case  and  no  disinfection,  as  was  the  condition  here 
at  first.  The  importer,  while  in  the  early  stages,  handles  with 
unclean  hands  food  for  others;  or  the  clothing  of  such  a  per- 
son gets  infected  and  is  handled;  there  need  be,  then,  no  diffi- 
culty in  completing  the  history.  It  follows  as  a  matter  of 
course." 

Contact  Typhoid  in  Spanish  War.  —  Probably  the  report 
of  Reed,  Vaughan  and  Shakespeare^  did  more  than  anything 
else  to  call  attention  to  the  importance  of  contact  infection 
in  the  epidemiology  of  this  disease.    This  commission  found 

'  Abst.  of  Rep.  on  the  Origin  and  Spread  of  Typhoid  Fever  in  U.  S. 
Military  Camps  during  the  Spanish  War  of  1898,  Wash.,  1900. 


INFECTION  BY  CONTACT  129 

that  infected  water  played  little  part  in  the  development  of 
typhoid  fever  in  the  camps.  They  also  found  that  probably 
every  regiment  brought  into  camp  one  or  more  mild  unrec- 
ognized cases  or  carriers,  and  that  these  were  the  starting 
points  of  outbreaks.  It  was  shown  that  the  fever  was  not 
evenly  distributed  through  the  regiments,  but  was  more  or 
less  localized  in  companies  or  squads  (p.  Ill  et  seq.). 

While  they  attributed  a  certain  amount  of  the  disease  to 
carriage  by  flies  and  by  dust,  they  considered  contact  infec- 
tion from  man  to  man  the  most  important  cause.  Of  1608 
cases  especially  studied,  and  which  were  accurately  located 
as  to  place  and  time,  35.01  per  cent  were  directly  connectible 
and  27.79  per  cent  indirectly  connectible  attacks;  total  con- 
nectible attacks,  62.80  per  cent  (p.  184).  Owing  to  the  unsat- 
isfactory methods,  or  lack  of  method,  of  excreta  disposal,  the 
shoes,  clothing  and  hands  of  the  men,  as  also  the  blankets 
and  tentage,  became  more  or  less  soiled  with  excreta,  and 
infection  of  the  men  became  easy,  and  in  fact  unavoidable. 
Men  detailed  as  hospital  orderlies  were,  after  they  had  per- 
formed the  duty  of  emptying  bedpans,  seen  to  go  directly 
to  their  meals  without  washing  their  hands,  and  even  to  dis- 
tribute food  to  their  comrades. 

In  South  Africa.  —  Similar  conclusions  were  arrived  at  by 
the  surgeons  who  studied  typhoid  fever,  which  proved  equally 
disastrous  to  the  English,  in  the  Boer  War,  but  on  the 
whole,  however,  the  English,  while  recognizing  the  impor- 
tance of  contact  infection,  did  not  place  so  much  stress 
upon  it  as  did  the  Americans.' 

Contact  Tjrphoid  in  Civil  Life.  —  Outbreaks  in  civil  life 
have  of  late  frequently  been  attributed  largely  to  contact 
infection.  Winslow"  reported  an  out})reak  in  Newport,  R.  I., 
which  probably  had  its  origin  in  an  infected  well,  but  wliich 

>  Col.  Lanc-Nottcr,  Tr.  Epidemiol.  Hoc,  Lond.,  1904,  XXIII,  149; 
J.  Roy.  Army  Med.  Corps,  Lond.,  1905,  IV,  587,  693;  Tooth,  Brit.  M. 
J.,  Lond.,  1901,  I,  642. 

»  Winslow,  Technology  Quarterly,  1901,  XIV. 


130         THE  SOURCES  AND  MODES  OF  INFECTION 

was  continued  by  contact  infection.  He  coined  the  word 
"  prosedemic  "  to  describe  this  extension  of  the  disease  from 
case  to  case.  Water-borne  and  milk-borne  outbreaks  of 
typhoid  fever  usually  develop  suddenly,  a  large  number  of 
cases  being  reported  within  a  short  time.  That  they  do  not 
end  so  suddenly  but,  even  after  the  infected  water  and  milk 
are  eliminated,  continue,  decreasing  gradually,  is  a  phenome- 
non which  becomes  apparent  from  the  examination  of  the 
charts  of  such  outbreaks.  This  prolongation  of  the  outbreak 
is  due  to  the  prosedemic  infection  of  Winslow,  and  has  been 
noted  by  Whipple  ^  for  water  outbreaks,  and  by  Trask^  for 
milk  outbreaks.  During  a  water-borne  outbreak  at  Lincoln, 
England,  from  50  to  60  per  cent  of  the  cases  were  due  to 
personal  contact.^ 

Municipal  Outbreaks.  —  Many  local  outbreaks  have  been 
believed  to  be  due  almost,  if  not  quite,  exclusively  to  contact 
infection.  Such  an  outbreak  was  reported  by  Weston  and 
Tarbett  in  Knoxville,*  Jordan  in  Winnipeg,^  Magrath  in 
Springfield,"  Noetel  in  Beuthen,^  and  Weil  in  Rathsweiler.^ 
Freeman^  states  that  the  majority  of  the  outbreaks  in  the 
smaller  towns  of  Virginia  appear  to  be  due  to  contact  infec- 
tion. The  authority  of  Koch  has  done  much  to  direct  atten- 
tion to  the  importance  of  contact  infection  in  the  spread  of 
typhoid  fever  in  civil  life.  In  a  report  on  a  village  outbreak 
in  Trier  ^"^  he  says  that  small  country  epidemics  will  usually 

1  Whipple,  Typhoid  Fever,  1908,  209. 

2  Trask,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 
No.  41,  38. 

3  Pub.  Health,  Lend.,  1905,  XVIII,  129. 

*  Weston  and  Tarbett,  Am.  Pub.  Health  Ass.  Rep.,  1907,  XXXIII, 
Pt.  1,  63. 

'  Jordan,  Abst.  in  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  563. 

"  Magrath,  Am.  J.  Pub.  Hyg.,  Bost.,  1905,  I,  467. 

'  Noetel,  Ztschr.  f.  Hyg.u.Infectionskrankh.,  Loipz.,  1904,  XLVII,211. 

'  Weil,  Med.  News,  N.  Y.,  1904,  LXXXIV,  467. 

*  Freeman,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  1263. 
""  Koch,  Die  Bekampfung  des  Typhus,  Berlin,  1903. 


IXFECTIOX  BY  COXTACT  131 

be  found  to  be  due  to  this  mode  of  infection.  In  the  particu- 
lar outbreak  investigated  all  the  cases  were  found  to  be  due 
to  contact,  that  is,  to  the  direct  transfer  from  person  to  per- 
son, and  the  source  was  in  most  instances  unrecognized  mild 
cases,  often  in  children.  He  then  describes  conditions  very- 
much  like  those  reported  by  Sedgwick.  Fecal  matter  was 
observed  in  the  dooryards  where  it  could  readily  infect  the 
children  playing  about,  and  would  certainly  be  carried  indoors 
on  their  shoes. 

Fulton,^  Egbert "  and  others  have  shown  that  tj'phoid  fever 
prevails  far  more  extensively  in  the  country  than  in  the  city. 
Formerly,  when  less  was  known  about  the  etiology  of  the 
disease,  polluted  well  water  was  believed  to  be  the  chief  factor 
in  its  causation,  but  it  now  appears  that  it  is  far  more  likely 
to  depend  on  contact  infection. 

In  Hospitals.  —  Typhoid  fever  frequently  develops  in  hos- 
pitals and  other  institutions,  presumably  by  contact  infec- 
tion. Occasionally  explosive  outbreaks  due  to  infected  milk 
or  food  are  observed,  but  many  institutional  outbreaks  are 
characterized  by  a  slow  and  irregular  development  of  cases. 
The  disease  chiefly  attacks  those  who  are  brought  in  close 
contact  with  the  sick,  physicians  and  especially  nurses.  Fifty 
or  sixty  years  ago  few  cases  of  hospital  infection  were  re- 
corded. It  is  suggested  that  this  may  have  been  due  to  the 
fact  that  nurses  in  tho.se  days  were  usually  women  well  along 
in  years,  and  therefore  not  so  susceptible  to  the  disease,  and 
usually,  perhaps  owing  to  the  greater  prevalence  of  the  dis- 
ease, immune.  During  recent  years  typhoid  fever  among 
nurses  and  ward  tenders  has  been  quite  common.  Joslin 
and  Ovcrlandcr  ^  state  that  26  of  322  nurses  at  the  Mas- 
sachusetts General  Hospital,  and  12  of  94  ward  tenders,  con- 
tracted typhoid  fever  while  on  duty.  It  is  said  that  in  the 
London  hospitals  typhoid  fever  is  twenty  times  as  common 

'  Fulton,  J.  Am.  M.  Ass.,  Chicago,  1904,  XLII,  73. 

*  Egbert,  Am.  Med.,  Phila.,  190.5,  IX,  649. 

»  Joslin  and  Overlander,  Boston  M.  &  S.  J.,  1907,  CLVII,  428. 


132         THE  SOURCES  AND  MODES  OF  INFECTION 

among  nurses  as  among  women  of  the  same  ages  in  other 
occupations/  Goodall  ^  says  that  during  the  j^ears  1892- 
1899  there  were  treated  in  the  London  hospitals  5913  typhoid 
patients,  and  100  attendants  contracted  the  disease.  In  four 
hospitals  not  admitting  typhoid  fever  no  cases  developed. 
Schuder,^  Neufeld/  McCrae,^  Talayrach,*^  Edsall  ^  and  others 
have  reported  an  excessive  prevalence  of  typhoid  fever  among 
the  attendants  on  cases  of  this  disease  in  hospitals,  and  they 
have  also  noticed  numerous  instances  in  which  it  has  devel- 
oped among  other  patients.  Nurses  and  others  infect  their 
hands  while  caring  for  typhoid  patients,  and  then  without 
washing  the  hands,  or  after  careless  washing,  infect  their 
own  mouths  directly,  or  by  handling  their  food  and  drink. 
Through  the  same  carelessness  they  also  infect  other  patients. 
Neufeld  refers  to  the  transfer  of  the  germs  on  a  thermometer 
and  in  a  bath.  Edsall  has  seen  a  nurse  given  the  double 
duty  of  emptying  the  bedpans  of  typhoid  cases  and  pre- 
paring special  diet,  and  a  patient  was  observed  to  empty  a 
bedpan  and  then  proceed  to  his  dinner  without  washing  his 
hands.  Nurses  also  wipe  out  the  mouths  of  patients  with  a 
bit  of  gauze  on  the  finger,  a  procedure  which  was  believed  by 
Holt  to  be  one  of  the  means  of  spreading  gonorrheal  infec- 
tion in  the  Babies'  Hospital.  By  introducing  strict  cleanli- 
ness Edsall  was  able  to  stop  this  transference  of  the  disease. 
In  Other  Institutions.  —  Sometimes  quite  marked  out- 
breaks occur  in  institutions,  due  presumably  to  contact  in- 
fection. Usually  water,  milk  and  other  food  as  sources  of 
infection  can  be  excluded,  and  the  irregular  and  slow  devel- 
opment of  the  cases,  and  perhaps  the  discovery  of  carriers  or 

1  Pub.  Health,  Lond.,  1905,  XVIII,  142. 

*  Goodall,  Trans.  Epidem.  Soc,  Lond.,  1900. 

^  Schuder,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  XXXVIII,  251. 

*  Neufeld,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1903,  II,  296. 
»  McCrae,  Mod.  Med.  [Osier],  Phila.  &  N.  Y.,  1907,  II,  82. 

*  Talayrach,  Arch.  d.  med.  et  de  pharm.  milit.,  Par.,  1903,  XLII,  393. 
'  Edsall,  Am.  J.,  M.  Sc,  Phila.,  1908,  n.  s.,  CXXXV,  469. 


INFECTION  BY  CONTACT  133 

missed  cases,  renders  the  extension  of  the  disease  by  per- 
sonal contact  highly  probable.  In  an  almshouse  in  New 
Haven/  37  cases  occurred  during  a  period  of  some  months. 
Mild  cases  were  concealed  and  worked  in  the  kitchen,  and 
it  was  impossible  to  teach  the  inmates  cleanly  habits.  At  a 
soldiers'  home  at  Lafayette,  Indiana,  there  were  65  cases 
due  to  contact  infection,  probably  chiefly  from  the  physician.^ 
At  the  State  Hospital  for  the  Insane  at  Trenton  there 
occurred  between  April  8  and  August  13,  1907,  80  cases 
with  16  deaths,  due  in  all  probability  to  contact  infection, 
largely  in  the  kitchen  and  pantry.^  Ravenel  *  reports  an 
outbreak  in  a  boarding  house  at  the  University  of  Wisconsin, 
where  41  cases  developed,  probably  as  the  result  of  a  patient 
working  in  the  pantry  during  the  prodromal  period  of  his 
illness.  Sedgwick^  reports  the  case  of  a  chambermaid,  and 
also  of  a  laundress,  who  contracted  typhoid  fever  from 
handling  soiled  linen.  A  waitress,  also,  who  ate  bread  cut 
by  the  other  two,  developed  the  disease.  Wolcott  tells  of 
the  matron  of  a  hospital  who  caught  the  disease  from  han- 
dling infected  bedding  and  neglecting  to  wash  the  hands. 
McCrae®  reports  an  instance  of  infection  from  careless  han- 
dling of  typhoid  cultures  in  the  laboratory,  and  a  similar 
case  occurred  in  an  insane  asylum  at  Northampton,  Mass.^ 
Dr.  Mann  tells  me  that  a  number  of  nurses  eating  at  the 
same  table  in  the  Homeopathic  Hospital  in  Boston  con- 
tracted typhoid  fever,  probably  from  a  waitress  whose  sister 
was  sick  with  the  disease,  and  who  herself  was  perhaps  a 
carrier. 

1  Rep.  Bd.  Health,  New  Haven,  1905,  6. 
»  Hurty,  J.  Am.  M.  A&s.,  Chicago,  1909,  LIII,  1263. 
»  Rep.  St.  Bd.  Health,  New  Jersey,  1907,  149. 
*  Ravenel  and  Smith,  K.  W.,  J.  Am    M.  Ass.,  Chicago,  1909,  LII, 
1635. 

»  Sedgwick,  .1.  M:uss.  A.s.s.  Hds.  Health,  Bost.,  1900,  X,  148. 
"  McCrae,  Mod.  Mod.  [Oslor],  Phila.  &  N.  Y.,  1907,  II,  82. 
'  Rep.  Bd.  Healtli,  Mass.,  Boat.,  1899,  762. 


134        THE  SOURCES  AND  MODES  OF  INFECTION 

Contact  on  Shipboard.  —  Many  of  the  instances  of  infec- 
tion by  carriers  referred  to  in  Chapter  II  -were  almost  cer- 
tainly the  result  of  contact  infection,  and  many  more  could 
be  easily  collected.  Occasionally  small  outbreaks  occur  on 
shipboard,  where  it  is  possible  to  exclude  all  modes  of  infec- 
tion but  contact.  Thus,  9  cases  on  an  Atlantic  liner  were 
traced  to  a  saloon  steward.^  On  the  United  States  ship  Con- 
necticut there  were  three  outbreaks  in  1907,  almost  certainly 
due  to  contact  infection." 

In  the  Family.  —  During  1908  I  noted  three  small  out- 
breaks of  typhoid  fever  in  Providence,  due  apparently  to  con- 
tact infection.  In  one  instance  there  were  10  cases  in  three 
closely  related  families,  in  another  8  cases  in  three  such 
families,  and  in  the  third  outbreak  there  were  7  cases  in 
two  families.  Such  family  outbreaks  are  noticed  in  Provi- 
dence nearly  every  year,  and  they  are  referred  to  so  often 
in  current  medical  literature  that  it  does  not  seem  necessary 
to  give  additional  references.  Contact  outbreaks  in  hotels 
and  boarding  houses,  as  well  as  in  various  public  institutions, 
are  also  frequently  reported.  Hill  in  Birmingham,  in  1898, 
traced  10  per  cent  of  the  typhoid-fever  cases  to  contact  with 
other  cases.  In  Manchester  in  the  same  year  about  13  per 
cent  were  traced  in  the  same  way,  and  in  1906,  36.8  per  cent. 
Edsall  attributed  27  per  cent  of  250  cases  to  contact,  and 
Forster  117  of  386  cases,  and  McCrae  68  of  500  cases.  It 
would  be  easy  to  prolong  the  discussion  and  show  that  med- 
ical men  are  everywhere  attributing  more  and  more  impor- 
tance to  contact  infection  in  this  disease.  It  is  to  be  noted 
that  in  few  of  the  reported  instances  of  contact  infection  is 
there  any  direct  and  conclusive  proof  that  the  disease  was 
caused  in  the  manner  alleged.  The  evidence  is  by  no  means 
so  convincing  as  to  mode  of  infection  as  it  is  in  so  many 
water-borne  and  milk-borne  outbreaks,  and  from  the  nature 
of  things  it  rarely  can  be  so. 

1  Rep.  Med.  Off.  Health,  Glasgow,  1907,  147. 

2  McDonnold,  Mil,  Surgeon,  Carlisle,  Pa.,  1908,  XXIII,  29. 


INFECTIOX  BY  CONTACT  135 

Evidence  of  Contact  Infection.  —  But  when  water  and  food 
as  vehicles  of  infection  are  excluded,  when  the  disease  devel- 
ops in  persons  who  are  in  contact  with  the  sick  or  with  car- 
riers, and  when  the  fingers,  possibly  or  perhaps  evidently- 
soiled  with  excreta,  are  seen  to  touch  food,  eating-utensils, 
and  sometimes  the  lips,  the  probability  of  the  development 
of  the  disease  in  this  manner  is  so  evident  that  observers 
are  constantly  seeing  in  contact  infection  the  cause  of  family, 
institutional  and  community  outbreaks  of  this  disease.  The 
importance  now  attributed  to  contact  infection  is  the  result 
of  a  careful  estimate  of  probabilities. 

Amount  of  Contact  Infection.  —  In  1908  there  were  11,375 
deaths  from  typhoid  fever  in  the  registration  area  of  the 
United  States,  which  doubtless  means  considerably  over 
100,000  cases.  The  registration  area  includes  about  one-half 
the  population  of  the  country.  While  a  certain  amount  of 
typhoid  fever  is  caused  by  milk,  it  must  be  a  very  small 
fraction  of  the  great  total.  As  will  be  shown,  milk  outbreaks 
are  usually  well  marked,  and  probably  not  a  very  great  deal 
of  milk-borne  infection  escapes  notice.  Again,  while  in  some 
cities  the  larger  part  of  the  typhoid  fever  is  due  to  infected 
water,  it  is  not  so  in  most  cities,  and  certainly  only  a  small 
part  of  the  total  typhoid  fever  in  the  country  can  be  traced 
to  such  a  source.  It  is  not  likely  in  my  own  city  for  instance 
that  more  than  20  per  cent  of  the  4300  cases  of  typhoid  fever 
during  the  past  twenty-five  years  have  been  due  to  infected 
water  or  milk;  and  infected  oysters,  celery,  etc.,  certainly 
play  a  very  unimportant  part  in  the  causation  of  the  disease. 
As  we  shall  see,  it  is  improbable  that  air-borne  infection 
or  dust  infection  is  of  any  moment  in  civil  life.  The  only 
other  important  source  of  typhoid  fever  which  has  been  sug- 
gested is  fly-borne  infection.  It  will  be  shown  also  that 
infection  by  means  of  flies  probably  accounts  for  only  a 
small  part  of  our  typhoid  fever.  By  exclusion,  then,  we 
are  led  to  the  conclusion  that  contact  infection  is  the  chief 
source  of  our  typhoid  fever. 


136         THE  SOURCES  AND  MODES  OF  INFECTION 

Why  should  we  not,  in  the  absence  of  direct  evidence  as 
to  other  modes  of  infection,  assume  at  once  that  contact, 
that  is,  the  more  or  less  direct  transfer  of  infective  material 
from  person  to  person,  is  the  principal  source  of  contagious 
disease  ?  Why  neglect  the  most  obvious  and  direct  mode 
of  transfer  in  favor  of  more  circuitous  paths  ?  There  are 
several  reasons  why  contact  infection  in  this  disease  has  been 
neglected. 

Why  Contact  Infection  has  been  Neglected.  —  One  reason 
has  been  the  undue  emphasis  laid  upon  other  modes  of  trans- 
mission. Formerly  air  infection  was  considered  of  great 
moment,  and  as  this  fell  into  disrepute,  undue  weight  was 
attached  to  water  and  milk  infection,  partly,  no  doubt,  because 
of  the  dramatic  character  of  so  many  outbreaks.  Another 
reason  for  doubting  the  importance  of  contact  infection  is 
the  prevalent  notion  that  typhoid  fever  is  essentially  an  intes- 
tinal disease,  and  that  it  must  be  caused  by  infected  food. 
It  now  appears  that  typhoid  fever  is  not  an  intestinal  disease, 
and  in  some  cases  the  intestines  are  not  involved  and  the 
feces  are  free  from  bacilli  during  the  whole  sickness.  But 
the  bacilli  are  found  in  the  blood  stream  in  the  earliest  stages, 
and  it  seems  to  be  more  likely  that  they  enter  the  circulation 
through  the  upper  part  of  the  alimentary  tract  than  through 
the  intestines  after  running  the  gauntlet  of  the  gastric  secre- 
t-ions. Even  if  it  be  denied  that  the  tonsils  and  stomach  are 
the  portals  of  entry  of  the  typhoid  bacilli,  it  is  highly  probable 
that  bacilli  taken  into  the  mouth  in  small  masses  find  their 
way  to  the  lower  part  of  the  alimentary  tract  by  means  of 
the  small  quantities  of  saliva  which  are  constantly  swallowed. 
It  has  certainly  been  demonstrated  that  tubercle  bacilli  are 
swallowed  and  thus  reach  the  intestines. 

People  are  not  Cleanly.  —  Then,  too,  contact  infection 
in  typhoid  fever  supposes  an  intimacy  with  the  most  offen- 
sive substances,  which  most  persons  would  vehemently  deny. 
Nevertheless  it  appears  that  the  fingers  of  human  beings, 
and  secondarily  everything  that  the  fingers  touch,  are  fre- 


INFECTION  BY  CONTACT  137 

quently  contaminated  with  excremental  matter.  The  colon 
bacillus  is  for  all  practical  purposes  a  good  test  for  the  pres- 
ence of  excrement,  and  it  is  somewhat  of  a  shock  to  learn  that 
it  is  found  on  the  hands  of  five  to  ten  per  cent  of  ordinarily 
cleanly  people.  Winslow  ^  and  Hall,^  while  studying  the  dis- 
semination of  typhoid  fever  by  carriers,  recovered  fecal, 
bacteria  from  the  finger  nails  and  hands  after  the  usual  pro- 
cedures following  the  use  of  the  closet  and  toilet.  An  inspec- 
tion of  the  privies  or  water-closets  in  railway  stations, 
factories,  shops  and  tenement  houses  shows  that  they  usually 
present  evidence  of  contamination  with  feces  and  urine,  and 
in  many  instances  are  constantly  in  a  horribly  filthy  condition. 
It  is  only  in  the  better  class  of  hotels  and  residences  that  these 
apartments  are  kept  in  even  an  apparently  cleanly  condition, 
and  this  is  only  by  dint  of  constant  vigilance  and  frequent 
cleansing.  There  can  be  no  doubt  that  even  very  careful 
people  frequently  infect  the  seat,  their  fingers,  the  pull,  the 
door,  etc.,  and  that  in  a  large  proportion  of  privies  and  water- 
closets  the  users  almost  certainly  infect  their  fingers  with  at 
least  traces  of  their  own  or  others'  excremental  matter.  Yet 
how  many  persons  are  there  who  invariably  wash  the  hands 
after  the  use  of  a  closet  ?  How  many  make  it  a  rule  never 
to  put  the  fingers  in  the  mouth  ?  Yesterday  I  saw  a  workman 
carrying  a  can  of  beer  to  his  friends.  His  thumb  was  im- 
mersed a  couple  of  inches  in  the  beverage.  Had  he  washed 
his  hands  after  leaving  the  barroom  water-closet  ?  At  a 
recent  sanitary  convention  I  noticed  the  colored  waiter  stick 
his  finger  into  a  glass  which  he,  however,  did  not  remove,  and 
which  the  speaker  soon  drank  from.  What  was  the  recent 
history  of  that  finger  ?  Does  the  fruit  petldler  wash  his  hands 
after  using  the  tenement  privy  before  he  ventures  to  sort  his 
fruit  ?  Do  the  waitress,  the  milk  peddler,  the  candy  seller, 
the  Pullman  porter,  the  soda-water  clerk,  the  baker's  boy, 
the  delicatessen  man  always  wash  the  hands  before  taking 

'  Winslow,  J.  Mtiss.  Ass.  Hds.  Health,  Host.,  1903,  XIII,  144. 
*  Hall,  Rep.  Med.  Ofif.  Health,  Bristol,  Eng..  1908,  27. 


138         THE  SOURCES  AND  MODES  OF  INFECTION 

up  their  work?  Are  the  toilets  in  their  places  of  business 
so  cleanly  that  such  a  precaution  is  not  necessary  ?  How- 
ever shocking  it  may  seem,  it  is  certain  that  it  requires  only 
a  little  observation  to  demonstrate  that  the  path  from  intes- 
tines to  mouth  is  not  always  a  circuitous  one. 

Contact  with  Carriers.  —  Until  recently  it  would  have 
been  argued  that  contact  infection  is  not  an  important  factor 
in  typhoid  fever  because  only  a  small  proportion  of  the  cases 
can  be  shown  to  have  been  in  contact  with  this  disease,  and 
because  the  large  proportion  of  cases  of  this  fever  are  more 
or  less  isolated  in  their  homes  because  of  the  sickness.  But 
we  now  know  that  there  are  vast  numbers  of  mild  unrecog- 
nized cases,  and  most  important  of  all,  that  the  number  of 
carriers  is  very  great.  There  are  doubtless  200,000  cases  of 
this  disease  in  the  United  States  each  year.  If  only  3  per 
cent  of  these  become  chronic  carriers,  and  if  a  carrier  remains 
such  only  three  years,  we  should  have  a  carrier  population 
of  18,000  persons,  practically  all  unknown  and  taking  no  pre- 
cautions against  infecting  others.  If  we  add  to  these  the 
25  per  cent  of  convalescents,  who  for  some  weeks  are  excret- 
ing the  bacilli  in  their  urine,  it  appears  that  there  is  a  very 
respectable  army  of  unrecognized  sources  of  typhoid  infection. 

At  present  we  have  no  definite  knowledge  of  the  origin  of 
the  larger  number  of  our  cases  of  typhoid  fever.  In  view 
of  the  almost  universal  careless  habits  of  the  people,  and 
the  great  number  of  carriers,  why  not  adopt  as  a  working 
hypothesis  the  most  obvious  source  of  infection,  infection  by 
contact  ? 

Danger  from  Privies.  —  This  view  that  contact  infection 
is  the  most  important  factor  in  the  causation  of  this  disease, 
is  borne  out  by  the  observation  that  the  more  promptly  and 
effectively  human  excrement  is  disposed  of,  the  less  chance 
there  is  for  contact  infection  and  the  less  the  disease  prevails. 
When  the  disposal  is  exceptionally  bad,  as  in  army  camps, 
lumber,  mining  and  railroad  camps,  then  this  disease  is  al- 
most always  very  common.    In  thoroughly  sewered  and  clean 


IXFECTION  BY  COXTACT  139 

cities,  provided  the  water  and  milk  are  not  contaminated, 
typhoid  fever  is  comparatively  rare.  The  privj'  vault  stores 
up  fecal  matter  on  the  premises  and  is  rarely  kept  as  clean 
as  a  water-closet,  and  the  area  around  privies  is  often  filthy 
also.  It  has  often  been  noted  that  the  removal  of  privy 
vaults  has  been  followed  by  a  decrease  in  typhoid  fever.  In 
Providence  the  disease  fell  off  forty  per  cent  after  most  of  the 
privy  vaults  were  abolished.  Many  other  American  cities  in 
which  typhoid  fever  is  not  maintained  b}"  a  polluted  water 
supply,  show  a  steadily  decreasing  prevalence  of  this  disease 
as  privy  vaults  are  gotten  rid  of.  In  England  Pringle^  has 
shown  that  in  fourteen  towns  with  middens  the  typhoid  rate 
was  0.25  per  1000,  while  in  fourteen  water-closet  towns  it 
was  0.19.  In  Ipswich  there  was  a  marked  decrease  in  typhoid 
fever  following  the  removal  of  the  middens.^  A  similar  de- 
crease was  noted  in  Oldham,  Leicester^  and  other  cities.  On 
the  other  hand  more  ''  pail  closets  "  remain  in  Nottingham 
than  in  most  English  cities,  and  to  this  Boobbyer^  attributes 
the  fact  that  typhoid  fever  has  decreased  less  in  that  town 
than  in  the  other  great  towns  of  England.  Like  reports  of 
a  decrease  in  the  disease  following  removal  of  privies  come 
from  such  widely  separated  places  as  Winnipeg  ^  and  Mel- 
l)ourne.® 

There  are  also  numerous  reports  to  the  effect  that  in  the 
same  town  typhoid  fever  is  much  more  common  in  houses 
without  water-closets  than  in  those  with  them.  This  may 
be  due  in  part  to  the  storing  of  fecal  matter  on  the  premises 
of  the  former,  and  it  may  be  due  also  to  the  fact  that  houses 
with  privies  are  usually  of  a  poorer  class,  and  the  inhabitants 
less  cleanly  in  their  personal  habits,  or  to  other  reasons;  but 

'  PrinKlo,  Pub.  Health,  Tx)ncl.,  1902-03,  XV,  630. 

2  Puf).  Hoalth,  I^nd.,  190.S-09,  XXII,  414. 

'  Rep.  Mod.  Off.  Health,  Leieester,  Kng.,  190S,  29. 

♦  Boobl)yer,  liep.  Health  of  Nottingham,  190S,  53. 
6  Rep.  Dept.  Pub.  Health,  Winnipeg,  UMiS,  4. 

•  Jamieson,  J.,  Australas.  M.  Gaz.,  Sydney,  1903,  XXII,  56. 


140         THE  SOURCES  AXD  MODES  OF  INFECTION 

these  facts  of  typhoid  distribution  accord  with  the  view  that 
the  disease  is  largely  spread  by  contact  from  person  to 
person.  In  Birmingham/  the  incidence  of  typhoid  fever  in 
"  pail  "  and  water-closet  houses  was  as  65  to  43,  and  there 
has  been  a  steady  decrease  in  the  disease  as  the  "  pail 
closets"  have  been  abolished.  In  Nottingham  there  was  (in 
ten  years)  1  case  in  each  37  houses  with  privies,  and  1  in 
each  558  water-closet  houses;  in  Salford  it  was  1  to  20  and 
1  to  42  respectively,^  and  in  Gorton  the  cases  were  two 
or  three  times  as  numerous  in  privy  houses  as  in  water- 
closet  houses.^  At  Leigh, ^  typhoid  fever  was  four  times 
as  prevalent  among  colliery  workers  as  among  the  rest  of  the 
population,  owing,  in  the  opinion  of  the  inspector,  to  the  filthy 
mode  of  excreta  disposal  in  the  mines.  In  Glasgow^  second- 
ary cases  of  the  disease  developed  in  23  per  cent  of  the  cases 
in  houses  with  privies  and  in  6  per  cent  of  the  cases  in  houses 
with  water-closets. 

Every  one  who  has  had  practical  experience  in  sanitary 
inspection  work  knows  that  privy  vaults  not  only  serve  as 
storehouses  for  excrement,  but  their  presence  encourages  its 
careless  disposal  in  the  yards  and  on  ash  heaps.  The  filthy 
condition  of  the  ground  about  the  houses,  leading  to  contami- 
nation of  feet  and  hands  of  children,  as  reported  by  Sedgwick 
and  by  Koch,  is  rarely  noticed  on  premises  provided  with 
water-closets.  It  may  be  urged  that  the  excess  of  typhoid 
fever  in  privy  towns  is  due  to  infection  by  flies  rather  than 
infection  by  contact,  and  this  may  be  true  to  some  extent; 
but  if  flies  were  the  chief  factor  we  should  scarcely  expect 
a  great  difference  between  water-closet  and  privy  houses  in 
the  same  town.     So  also  the  infection  of  miners,  as  noticed 

»  Rep.  Health  of  Birmingham,  1906,  49,  and  1908,  49. 
2  Pringle,  Pub.  Health,  Lond.,  1902-03,  XV,  630. 
'  Martin,  Pub.  Health,  Lond.,  1904-05,  XVH,    709. 
*  Sweeting,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lend.,  1907-08,  XXXVII, 
57. 

s  Rep.  Med.  Off.  Health,  Glasgow,  1902,  97. 


INFECTION  BY  CONTACT  141 

by  Sweeting,  cannot  be  due  to  flies.  In  Pro\adence  after  the 
removal  of  privies  the  decrease  in  tjTDhoid  fever  was  as  great 
in  winter,  when  there  were  no  flies,  as  during  the  fly  season. 

Amebic  Dysentery.  —  There  is  no  reason  why  amebic 
dysentery  may  not  be  transmitted  by  personal  contact,  but 
if,  as  is' generally  believed,  the  ameba  is  quite  widely  dis- 
tributed in  the  soil,  it  is  likely  that  in  countries  where  the 
disease  is  endemic,  man  is  the  least  common  source  of  infec- 
,  tion.  Nevertheless  cases  do  develop  from  contact  with  other 
cases.  Lemoine^  has  reported  such  infections  in  France,  in 
one  instance  at  least,  probably  due  to  the  use  of  the  same 
bedpan,  douche,  etc.  The  infecting  case  was  a  carrier  of 
ten  years'  standing.  Allan^  writes  that  in  Charlotte,  N.  C, 
he  observed  four  cases  of  amebic  dysentery  which  he  believed 
were  due  to  contact  with  chronic  carriers. 

Bacillary  Dysentery.  —  Bacillary  dysentery,  like  typhoid 
fever,  is  a  great  scourge  of  military  life,  and  outbreaks  of  a 
serious  character  are  not  rare  in  in-stitutions  such  as  hospitals 
for  the  insane.  The  bacillus  is  found  in  the  feces  of  the 
patients  and  also  in  convalescents.  There  is  every  reason 
for  believing  that  this  disease,  like  typhoid  fever,  is  frequently 
spread  by  more  or  less  direct  contact.^  Conradi  *  described 
a  village  outbreak  near  Metz  where  70  cases  occurred  during 
a  period  of  three  months.  Several  carriers  were  found  in 
infected  families,  and  conditions  favoring  contact  infection 
were  noted,  very  similar  to  those  observed  in  the  outbreaks 
of  typhoid  fever  studied  by  Koch  in  Trier.  Dodge  ^  reports 
the  case  of  a  laboratory  worker  who  got  some  of  a  culture 
of  the  dysentery  bacillus  in  his  eye;  the  tears  ran  profusely 
and  were  swallowed,  and  in  twenty-four  hours  an  attack  of 

'  Lemoine,  Bull,  et  mem.  Soc.  med.  de  hop.  de  Par.,  1908,  3  s.,  XXV, 
640. 

»  Allan.  Med.  Rec,  N.  Y.,  1910,  LXXVII,  63. 

'  Shiga,  Mo(l.  M(h1.  [Oslerl,  Phila.  &  N.  Y.,  1907,  II,  781;  Scheube, 
Diseases  of  Warm  Chmatcs,  2d  VA.,  Phila.,  466. 

*  Festschrift  von  Robert  Koch,  1903,  5.5.5. 

*  Dodge,  Am.  Pub.  Health  Aas.  Rep.,  1905,  XXX,  310. 


142         THE  SOURCES  AND  MODES  OF  INFECTION 

dysentery  developed.  An  outbreak  of  49  cases,  developing  in 
the  characteristic  slow  irregular  manner  of  contact  outbreaks, 
was  reported  in  the  Connecticut  Hospital  for  the  Insane.^ 
Kruse^  reports  a  similar  outbreak  in  Germany,  and  two  in 
Holland.  Epidemic  dysentery  is  quite  common  in  hospitals 
for  the  insane,  and  its  prevalence  is  explained  as  due  chiefly 
to  contact  infection,  for  the  carelessness  of  many  patients 
and  the  impossibility  of  controlling  their  habits  offer  every 
opportunity  for  this  sort  of  diffusion.^ 

Cholera  and  Contact.  —  If  typhoid  fever  and  dysentery 
are  spread  by  means  of  contact  infection,  we  should  expect 
that  cholera  would  be.  That  less  is  written  about  it  is  due 
probably  to  the  fact  that  in  recent  years  less  attention  has 
been  paid  to  cholera  than  to  the  more  common  diseases. 
The  literature  relating  to  typhoid  fever  has  of  late  been  many 
times  more  voluminous  than  that  relating  to  cholera.  Never- 
theless most  writers  attribute  some  importance  to  contact 
infection  in  this  disease,  and  some  consider  it  an  etiological 
factor  of  very  great  importance.  The  filthy  conditions  of  vil- 
lage life  described  by  Sedgwick  in  America  and  Koch  in  Ger- 
many as  giving  rise  to  typhoid  fever,  are  far  surpassed  in 
danger  by  the  habits  of  vast  numbers  of  the  poorer  people 
who  dwell  in  cholera-infested  countries.  The  opportunities 
for  the  direct  transference  of  fecal  matter  from  person  to 
person  are  far  greater  in  Asiatic  countries  than  they  are  with 
us,  and  a  number  of  writers  have  emphasized  the  part  played 
by  personal  contagion  in  this  disease.    Gotschlich  *  refers  to 

1  Rep.  St.  Bd.  Health,  Connect.,  1903,  234. 

2  Kruse,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  370,  386. 

^  See  Reports  of  Commissioners  in  Lunacy  (Eng.)  since  1903;  also 
Heuser,  Deutsche  med.  Wchnschr.,  1909,  XXXV,  1694;  Ryder,  Boston 
M.  &  S.  J.,  1909,  CLXI,  681;  Haenisch,  Ztschr.  f.  Hyg.  u.  Infections- 
krankh.,  Leipz.,  1908,  LX,  245;  Mott,  Tr.  Epidem.  Soc,  Lond., 
1901-02,  and  Arch.  Neurol.  Path.  Lab.,  Lond.  Co.  Asyl.,  Lond.,  1903, 
II,  735;  Prior,  Australas.  M.  Cong.  Tr.,  Victoria,  1909,  III,  383. 

*  Gotschlich,  KoUe  and  Wassermann,  Handbuch  [etc.],  Jena,  1904, 
IV,  108. 


INFECTION  BY  CONTACT  143 

this  factor,  and  a  number  of  our  officers  in  the  Philippines 
have  dwelt  upon  its  importance.  Woodruff^  says  that  while 
infected  water  played  some  part  in  the  great  epidemic  in 
Manila,  the  filthy  habits  of  the  people  were  the  chief  cause 
of  the  extension  of  the  disease.  He  speaks  of  an  outbreak 
of  eighty  cases  in  a  provincial  town  due  to  food  prepared  in 
Manila  by  a  caterer  who  soon  died  of  cholera.  Heiser'  con- 
siders that  the  handling  of  foodstuffs  and  of  the  leaves  in 
which  the  betel  nut  is  wrapped,  by  dealers  and  prospective 
purchasers,  is  one  of  the  chief  ways  in  which  cholera  is  spread, 
and  McLaughlin^  considers  the  "carrier"  with  filthy  habits 
the  greatest  source  of  danger.  He  says  that  contact  infection 
of  visitors  in  the  houses  of  the  sick  is  a  common  means  of 
disseminating  the  disease.  Schumburg  *  reported  several 
small  outbreaks  of  cholera  near  Hamburg  caused  by  contact 
infection.  Shakespeare^  reports  several  instances  in  which 
cholera  was  apparently'  caused  by  handling  soiled  linen,  some 
of  which  might  perhaps  be  considered  rather  as  examples  of 
fomites  infection.  Macrae*  reports  the  infection  of  hospital 
nurses  with  cholera  in  a  manner  similar  to  the  infection  of 
nurses  with  typhoid  fever. 

Diarrhea.  —  Newsholme'  believes  that  much  infantile 
diarrhea  is  due  to  direct  contact  infection  in  the  home, 
rather  than  to  extraneous  bacteria  in  the  milk,  and  he 
suggests  that  it  is  brought  about  by  "  sucking  infective 
matter  from  dirty  fingers,  from  dummy  teats  and  in  other 
ways."  Many  other  English  health  officers  agree  with  News- 
holme  in  thinking  that  contact  infection,   entirely  outside 

1  Woodruff,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  11()0. 
»  Hei.ser,  J.  Am.  M.  Ass.,  Chicago.,  1907,  XLVIII,  856. 
'  McLaughlin,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1153. 

*  Schumburg,  Ztschr.  f.  arztl.  Fortbild.,  Jena,  1905,  II,  567. 

'^  Shakespeare,  Rep.  on  Cholera  in  Europe  and  India,  U.  S.  Gov. 
Printing  Office,  ISW,  SI. 

•  Macrae,  Indian  M.  (la/..,  1909,  XLIV,  301. 

'  Newsholmc,  J.  Ilyg.,  Cambridge,  1906,  VI,  139. 


144  THE  SOURCES  AND  MODES  OF  INFECTION 

the  milk,  plays  no  inconsiderable  part  in  the  causation  of 
diarrhea.' 

Hookworms.  —  Diseases  caused  by  worms  are  only 
incidentally  referred  to  in  this  book,  but  there  is  one  of 
these  which  is  of  considerable  interest  in  this  connection. 
Hookworm  disease,  in  some  respects,  bears  a  considerable 
resemblance  to  bacterial  infections,  since  constitutional 
symptoms,  as  marked  anemia  and  debility,  are  present,  due 
presumably  to  the  formation  of  toxic  substances,  as  well  as  to 
the  direct  loss  of  blood.^  Moreover,  immunity  seems  to  be 
developed,  and  the  worms  are  often  found  in  persons  who 
present  no  symptoms.  Hookworm  disease,  which  had  been 
known  for  many,  years  in  Europe,  where  it  had  been  shown 
to  be  due  to  a  small  worm,  Anchylostoma  duodenalis,  was, 
as  a  result  of  scientific  work  following  the  Spanish  War, 
particularly  that  of  Ashford  in  Porto  Rico,  found  to  be 
very  prevalent,  not  only  in  the  West  Indies,  but  also,  as 
shown  by  Stiles,  in  our  southern  states.  Stiles,  however, 
found  that  our  disease  is  due  to  a  worm  shghtly  different 
from  the  European  species,  and  which  has  been  named 
Uncinaria  americana. 

The  disease,  known  now  as  uncinariasis,  or  anchylostomia- 
sis,  is  due  to  the  growth  of  the  worms,  which  are  about  half 
an  inch  long,  in  the  intestine,  where  they  fasten  themselves 
to  the  intestinal  wall,  and  not  only  suck  blood  themselves,  but 
also  cause  considerable  free  bleeding  from  the  wounds  which 
they  make.  '  The  eggs,  which  are  laid  in  the  intestine,  do  not 
there  develop,  owing  to  lack  of  oxygen,  but  hatch  soon  after 
the  feces  are  voided,  and  the  young  worms  then  pass  through 
several  stages  of  growth  in  moist  earth  or  mud. 

Until  recently  it  was  believed  that  human  infection  resulted 
from  drinking  water  containing  the  young  worms,  or  by  get- 

1  Naish,  Pub.  Health,  Lond.,  1909-10,  XXIII,  168;  Sandilands,  Proc. 
Roy.  Soc.  Med.  1910,  III,  Epidem.  Sec,  109. 

«  Stiles,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 
No.  10,  1903. 


INFECTION  BY  CONTACT  145 

ting  them  onto  fingers  or  into  food,  and  so  into  the  mouth. 
It  was  first  suggested  by  Looss  in  1898  that  infection  might 
take  place  through  the  skin,  and  he  believed  that  he  had 
himself  become  infected  in  that  way.  In  1901  he  proved  the 
correctness  of  his  surmises  by.  experiments.  Later  Grassi, 
Fieri  and  Noe  placed  a  few  drops  of  water  containing  worms 
upon  the  skin,  but  only  one  of  the  three  became  infected. 
In  1902  Looss  successfully  repeated  his  experiments.  It  had 
meantime  been  noticed  by  Bentley  and  Boycott  and  Haldane 
that  dermatitis  was  apt  to  be  found  in  regions  where  the 
disease  prevailed,  and  it  was  suspected  that  it  might  be  due 
to  the  passage  of  the  worms  through  the  skin.  Smith  ^  showed 
that  by  placing  infected  earth  on  the  arm,  not  only  was  infec- 
tion caused,  but  there  resulted  a  dermatitis  at  the  site  of  the 
application.  Ashford,  whose  careful  study  of  the  disease 
in  Porto  Rico,  and  whose  brilliant  success  in  curing  its  vic- 
tims give  his  opinion  great  weight,  believes  that  the  skin 
is  by  far  the  most  important  avenue  by  which  the  worms 
infect  the  body.^  Uncinariasis  is,  then,  par  excellence,  a  dis- 
ease due  to  contact  infection. 

Fortunately  the  disease  is  usually  easily  curable  under 
medical  treatment,  and  the  freeing  of  individuals  from  worms 
by  this  treatment  is  necessarily  an  important  part  of  the 
prevention  of  the  disease.  It  is  evident  from  the  mode  of 
infection  that  the  pollution  of  the  soil  with  human  feces  is 
the  principal  factor  in  the  spread  of  the  disease.  Froperly 
constructed  privies  or  water-closets,  with  the  ultimate  dis- 
posal of  the  fecal  matter  by  deep  burial,  or  some  other  means 
to  prevent  the  pollution  of  the  upper  layers  of  the  soil,  are 
the  essentials  of  prophylaxis. 

Contact  Infection  less  Easy  in  Some  Diseases  than  in 
Others.  —  Gonorrhea  is  a  disease  in  which  the  infecting  secre- 
tion is  not  likely  to  be  much  handled,  and  when  it  occurs 

»  Smith,  C.  A.,  J.  Am.  M.  Ass.,  Chicago,  190.5,  XLV,  1142. 
'  A.shfonl,    Hop.    of    Commission    on    Study    and    Treatment    of 
"Anemia"  in  Porto  Rico,  1904,  37. 


146         THE  SOURCES  AND  MODES  OF  INFECTION 

in  young  children  the  secretion  is  often  received  on  a  diaper. 
Yet  it  has  been  shown  in  the  preceding  pages  that  infantile 
gonorrhea  is  spread  exclusively  by  contact  infection.  Al- 
though the  children  themselves  take  little  part  in  the  spread 
of  the  disease  in  hospitals  where  they  are  isolated  from  one 
another,  and  although  nurses  and  physicians  have  been  shown 
the  danger  of  carrying  the  disease,  and  have  been  instructed 
to  take  the  greatest  precautions,  yet  this  disease  may  be 
maintained  for  months  in  an  institution  solely  by  means  of 
infection  borne  on  thermometers,  syringes,  etc.,  but  particu- 
larly on  the  hands  of  attendants. 

In  typhoid  fever  the  bacilli  are  contained  in  the  feces  and 
urine,  which  even  careless  people  are  supposed  to  avoid  touch- 
ing. Nevertheless  it  appears  that  the  fingers  of  careful  people, 
and  even  of  trained  nurses,  are  infected  in  this  manner,  and 
that  transfer  to  the  mouth  with  the  subsequent  development 
of  typhoid  fever  results.  There  is  much  evidence  that  this 
mode  of  transference  is  an  important,  if  not  the  most 
important,  factor  in  the  spread  of  this  disease. 

Contact  with  Saliva.  —  If  contact  infection  is  important 
in  such  diseases  as  gonorrhea,  typhoid  fever,  dysentery  and 
cholera,  in  which  the  infecting  material  is  not  constantly  at 
hand,  and  is  usually  strenuously  avoided,  how  much  more 
important  must  this  mode  of  transference  be  in  diseases  in 
which  the  specific  germs  are  found  in  the  secretions  of  the 
nose  and  mouth  or  in  the  sputum. 

Danger  from  Fingers.  —  Probably  the  chief  vehicle  for 
the  conveyance  of  nasal  and  oral  secretion  from  one  to  another 
is  the  fingers.  If  one  takes  the  trouble  to  watch  for  a  short 
time  his  neighbors,  or  even  himself,  unless  he  has  been  par- 
ticularly trained  in  such  matters,  he  will  be  surprised  to  note 
the  number  of  times  that  the  fingers  go  to  the  mouth  and 
the  nose.  Not  only  is  the  saliva  made  use  of  for  a  great 
variety  of  purposes,  and  numberless  articles  are  for  one  reason 
or  another  placed  in  the  mouth,  but  for  no  reason  whatever, 
and  all  unconsciously,  the  fingers  are  with  great  frequency 


IXFECTIOX  BY  COX  TACT  147 

raised  to  the  lips  or  the  nose.  Who  can  doubt  that  if  the 
sahvary  glands  secreted  indigo  the  fingers  would  contin- 
ually be  stained  a  deep  blue,  and  who  can  doubt  that  if 
the  nasal  and  oral  secretions  contain  the  germs  of  disease 
these  germs  will  be  almost  as  constantly  found  upon  the 
fingers?  All  successful  commerce  is  reciprocal,  and  in  this 
universal  trade  in  human  saliva  the  fingers  not  only  bring 
foreign  secretions  to  the  mouth  of  their  owner,  but  there  ex- 
changing them  for  his  own,  distribute  the  latter  to  everything 
that  the  hand  touches.  This  happens  not  once  but  scores 
and  hundreds  of  times  during  the  day's  round  of  the  indi- 
vidual. The  cook  spreads  his  saliva  on  the  muffins  and  rolls, 
the  waitress  infects  the  glasses  and  spoons,  the  moistened 
fingers  of  the  peddler  arrange  his  fruit,  the  thumb  of  the  milk- 
man is  in  his  measure,  the  reader  moistens  the  pages  of  his 
book,  the  conductor  his  transfer  tickets,  the  "  lady  "  the 
fingers  of  her  glove.  Every  one  is  busily  engaged  in  this  dis- 
tribution of  saliva,  so  that  the  end  of  each  day  finds  this 
secretion  freely  distributed  on  the  doors,  window  sills,  fur- 
niture and  playthings  in  the  home,  the  straps  of  trolley  cars, 
the  rails  and  counter  and  desks  of  shops  and  public  buildings, 
and  indeed  upon  everything  that  the  hands  of  man  touch. 
What  avails  it  if  the  pathogens  do  die  quickly?  A  fresh 
supply  is  furnished  each  day. 

Drinking  Cups.  —  Another  important  vehicle  of  transfer 
must  be  the  common  drinking  cup.  Davison'  estimated  that 
there  were  as  many  as  20,000  epithelial  cells  on  a  drinking 
glass  that  had  been  in  use  in  a  school  for  nine  days,  which 
well  illustrates  the  amount  of  infection  which  may  be  thus 
carried.  Cars,  steamboats,  hotels,  schools,  offices,  factories, 
theaters,  churches,  all  provide  a  common  vessel  from  which 
large  numbers  of  persons  drink,  thus  furnishing  an  almost 
ideal  method  by  which  perfectly  fresh  saliva  may  be  trans- 
ferred from  one  to  another.  Hundreds  of  thousands  of 
persons  must  be  each  day  in  this  manner  exchanging  the 
»  Davison,  Tech.  World  Mag.,  Chicago,  1908,  IX,  623. 


148         THE  SOURCES  AND  MODES  OF  INFECTION 

secretions  of  the  mouth.  When  travehng  in  the  steam  cars  I 
have  noted  the  shocked  expression  on  the  face  of  passengers 
as  a  fashionably  dressed  woman  was  seen  to  allow  her  pug 
dog  to  drink  from  the  common  glass,  —  not  a  pleasant  thing, 
of  course,  but  infinitely  less  dangerous  than  for  the  woman  to 
drink  from  it.  She  might  have  tuberculosis,  or  carry  diphthe- 
ria bacilli,  or  perhaps  even  have  mucous  patches  on  her  lips. 

Other  Kinds  of  Contact.  —  Besides  the  moistening  of  the 
fingers  with  saliva  and  the  use  of  the  common  drinking  cup, 
the  mouth  is  put  to  numberless  improper  uses  which  may 
result  in  the  spread  of  infection.  It  is  used  to  hold  pins, 
string,  pencils,  paper  and  money.  The  lips  are  used  to 
moisten  the  pencil,  to  point  the  thread  for  the  needle,  to  wet 
postage  stamps  and  envelopes.  Children  "swap"  apples, 
cake  and  lollipops,  while  men  exchange  their  pipes  and  women 
hatpins.  Sometimes  the  mother  is  seen  "cleansing"  the 
face  of  her  child  with  her  saliva-moistened  handkerchief, 
and  perhaps  the  visitor  is  shortly  after  invited  to  kiss  the 
little  one. 

Children  have  no  instinct  of  cleanliness,  and  their  faces, 
hands,  toys,  clothing  and  everything  that  they  touch  must 
of  necessity  be  continually  daubed  with  the  secretions  of  the 
nose  and  mouth.  It  is  well  known  that  between  the  ages  of 
two  and  eight  years  children  are  more  susceptible  to  scarlet 
fever,  diphtheria,  measles  and  whooping  cough  than  at  other 
ages,  and  it  may  be  that  one  reason  for  this  is  the  great 
opportunity  that  is  afforded  by  their  habits  at  these  ages 
for  the  transfer  of  the  secretions.  Infants  do  not  of  course 
mingle  freely  with  one  another,  and  older  children  do  not 
come  in  such  close  contact  in  their  play,  and  they  also  begin 
to  have  a  little  idea  of  cleanliness. 

Contact  Dangerous  because  of  Missed  Cases.  —  A  little 
observation  and  reflection  will  show  that  the  ways  are  num- 
berless in  which  fresh  secretion  of  nose  and  mouth  is  passed 
from  person  to  person.  Enough  has  been  written  to  demon- 
strate that  the  opportunities  for  contact  infection  are  suffi- 


INFECTION  BY  CONTACT  149 

ciently  numerous  to  account  for  the  spread  of  the  contagious 
diseases  without  invoking  an}'  other  mechanism.  The  chief 
objection  to  this  view  is  that  while  it  is  true  that  there  is  a 
considerable  interchange  of  secretions,  and  even  of  excretions, 
between  human  beings,  it  is  between  well  persons,  and  not 
between  the  sick  and  the  well.  That  this  objection  is  unten- 
able is  amply  demonstrated  b}^  the  evidence  presented  in 
Chapter  II.  There  can  no  longer  be  the  slightest  doubt  that 
there  are  large  numbers  of  mild  and  unrecognized  cases  of 
infectious  disease  mingling  freely  with  the  public,  and  that 
in  some  diseases,  and  perhaps  in  most,  there  are  also  larger 
numbers  of  perfectly  well  carriers  who  also  are  unknown. 
These  unrecognized  foci  are  clearly  numerous  enough  to 
cause,  by  their  contact  with  others,  the  recognized  cases.  The 
transfer  of  the  disease  by  fairly  direct  means  is  so  obvious 
and  easy  that  there  is  no  necessity  for  invoking  the  agency  of 
other  and  more  circuitous  modes  of  dissemination.  Indeed 
it  is  sometimes  said  that  the  arguments  here  presented  prove 
too  much,  and  that  if  carriers  were  as  numerous,  and  contact 
with  them  as  frequent,  as  is  here  alleged,  none  could  escape, 
and  infectious  disease  would  be  more  common  than  it  is. 
But,  as  was  stated  in  Chapter  II  and  on  page  111,  infection 
does  not  take  place  so  readily  as  is  generally  believed.  This 
is  demonstrated  clinically,  and  the  reasons  are  apparent. 
There  are  often  long  intervals  in  which  carriers  are  not  elimi- 
nating the  pathogenic  organism,  and  the  saliva  may  not  con- 
tain the  germs,  even  when  they  are  in  the  throat  and  nose. 
Germs  are  not  evenly  distributed  through  saliva,  sputum  or 
feces,  and  the  particle  transferred  may  be  free  from  them. 
The  infective  material  is  often  small  in  amount  and  spread 
in  a  thin  layer,  and  the  contaminated  organisms  speedily  die. 
Lastly,  small  numbers  of  pathogens  are  often,  perhaps  usu- 
ally, destroyed  by  the  body.  We  must  believe  that  usually 
continued  or  somewhat  massive  infection  is  necessary  to  cause 
disease,  but  that  nevertheless  sometimes  a  single  infection 
with  a  very  small  number  of  germs  suffices.    The  number  of 


150         THE  SOURCES  AND  MODES  OF  INFECTION 

unrecognized  foci  of  infection  in  human  beings,  the  oppor- 
tunities for  contact  infection,  and  the  natural  obstacles  to 
successful  infection,  appear  admirably  to  explain  many  other- 
wise inexplicable  phenomena  of  epidemiology. 

Bacteria  in  Mouth.  —  There  has  been  comparatively  little 
effort  made  to  determine  by  observation  the  frequency  with 
which  the  common  pathogens  are  actually  found  in  the  secre- 
tions of  the  nose  and  mouth  and  on  the  fingers  and  ob- 
jects which  can  serve  as  vehicles  of  contact  infection.  It 
is  assumed,  and  I  think  with  warrant,  that  the  germs  of 
many  of  our  common  diseases  are  thus  widely  distributed,  and 
the  assumption  corresponds  with  clinical  and  epidemiological 
facts.  But  the  subject  is  of  such  importance  that  it  is  very 
desirable  that  we  should  have  something  besides  assumptions, 
and  that  more  numerous  observations  should  be  made  as  to 
the  presence  of  pathogenic  bacteria  in  the  secretions  and 
upon  and  near  human  beings. 

On  Hands.  —  Reference  has  been  made  in  this  chapter, 
page  137,  to  the  finding  of  colon  and  typhoid  bacilli  on  the  fin- 
gers, but  the  examinations  have  been  very  few.  Pus-forming 
organisms  have  their  natural  habitat  on  the  mucous  surfaces 
and  in  the  skin,  and  the  experimental  work  of  the  surgeons  in 
improving  their  technique  has  demonstrated  a  very  wide  dis- 
tribution, and  has  shown  the  tremendous  importance  of  con- 
tact infection,  which  they  have  now  learned  most  successfully 
to  avoid. 

Bacteria  on  Cups,  Pencils.  —  Vincenzi  ^  found  diphtheria 
bacilli  in  the  holy  water  in  a  church  font.  Kinyoun,"  while 
searching  for  pathogens  in  railway  cars,  found  diphtheria 
bacilli  once  on  the  woodwork  and  once  on  a  drinking  glass, 
though  eighty-three  other  swabbings  were  negative.  Forbes, 
in  Rochester,  found  them  upon  a  drinking  glass  which  was 
believed  to  have  been  the  cause  of  a  small  outbreak.  This 
observation  has  been  frequently  referred  to,  and  though  I 

^  Vincenzi,  Semaine  med.,  1898. 

*  Kinyoun,  Med.  News,  N.  Y.,  1905,  LXXXVII,  193. 


IXFECTIOX  BY  COXTACT  151"" 

have  not  been  able  to  find  Forbes'  original  article,  Dr.  Goler, 
the  present  health  officer  of  Rochester,  informs  me  that  the 
facts  are  as  reported.  Williams*  recovered  diphtheria  bacilli 
from  pencils  moistened  by  the  lips  of  children  sick  with  the 
disease.  The  observations  referred  to  in  the  chapter  on 
fomites  show  that  the  germs  of  this  disease  are  rarely  found 
on  fomites  and  then  only  on  objects  that  have  been  recently 
and  grossly  infected. 

Tubercle  Bacilli  in  Mouth.  — Not  only  are  tubercle  bacilli 
found  in  enormous  masses  in  the  true  sputum,  but  they 
are  often  present  in  the  saliva  as  well.  Neild  and  Dunkley^ 
found  them  in  saliva  from  the  tip  of  the  tongue  in  29  of  50 
cases  of  pulmonary  tuberculosis.  Park  found  them  in  the 
saliva  of  10  of  15  cases,^  and  refers  to  Moller  recovering  them 
in  3  of  20  cases.  Le  Noir  and  Camus*  found  virulent 
tubercle  bacilli  in  the  nose  as  well  as  from  the  mouth  of 
tuberculous  cases. 

Pathogenic  Bacteria  on  the  Hands.  —  "^A'ith  the  present 
habits  of  human  beings  these  germs  must  be  constantly  trans- 
ferred to  the  fingers,  and  to  a  lesser  degree  to  everything  that 
the  fingers  touch.  Graziani'^  found  tubercle  bacilli  on  the 
hands  of  4  of  8  tuberculous  patients,  and  on  3  of  them  3 
hours  after  washing  with  soap  and  water.  He  also  obtained 
the  bacilli  from  the  hands  of  4  out  of  6  non-tuberculous 
patients.  After  shaking  hands  with  tuberculous  patients  he 
was  able  several  times  to  recover  the  bacilli  from  his  own 
hands.  Baldwin"  found  bacilli  on  the  hands  of  patients  in 
the  Adirondack  Sanatorium.  They  did  not  use  handker- 
chiefs.   Of  10  patients  seen  in  private  practice  8  had  tubercle 

1  Williams,  Scientific  Bull.  2,  1895,  Health  Dcpt.,  N.  Y.  City,  14. 
'  Neild  and  Dunkley,  Lancet,  Lond.,  1909,  I,  1096. 

*  Park,  Si.xth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  157. 

*  Le  Noir  and  Camus,  Comp.  rend.  Soc.  de  hiol.,  Par.,  1908,  LXV,  464. 

*  Graziani,  Ann  d'  Ig.  Sper.,  XV,  709,  referred  to  by  Rosenau,  Sixth 
Internat.  Cong,  on  Tuberc,  Wash.,  190S,  I,  28. 

«  Baldwin,  Tr.  Am.  Chmut.  Asa.,  1898,  XIV,  202. 


152         THE  SOURCES  AND  MODES  OF  INFECTION 

bacilli  on  their  hands.  The  other  two  were  exceptionally 
careful.  Preisich  and  Schiitz  ^  found  tubercle  baciUi  on  the 
hands  of  children  in  a  children's  hospital  at  Budapest.  Of 
66  examinations  of  the  dirt  from  under  the  finger  nails  14 
were  positive  under  the  microscope,  but  owing  to  the  death 
of  the  animals  from  sepsis  their  virulence  was  not  demon- 
strated. Of  the  14  positive  cases,  11  had  tuberculosis,  or 
were  associated  with  it,  while  of  the  52  negative  cases  only 
5  were  associated  with  tuberculosis.  Dieudonne^  by  inocu- 
lation demonstrated  tubercle  bacilli  on  the  hands  of  2  of 
15  children.  In  this  connection  may  be  mentioned  the 
experiment  of  Schumburg,^  in  which  he  rubbed  an  ose  of  a 
culture  of  bacteria  on  his  hands,  and  recovered  the  germs 
after  15  and  16  handshakes.  Ostermann,^  on  the  other  hand, 
does  not  consider  contact  infection  of  much  importance  in 
tuberculosis.  While  he  recovered  tubercle  bacilli  from  the 
hands  of  7  of  14  phthisical  patients  and  from  1  attendant, 
he  obtained  them  only  4  times  from  42  children  living  in 
tuberculous  families  and  2  times  from  the  floors  occupied  by 
these  families.  He  does  not  find  that  bacteria  are  transferred 
from  hand  to  hand  as  readily  as  have  other  observers.  He 
also  made  a  few  cage  experiments  with  guinea  pigs  to  show 
that  infection  by  contact  is  less  effective  than  infection  by 
air. 

It  scarcely  needed  the  experiments  of  Annett  at  Liverpool  ^ 
and  Higgins"  at  Birmingham  to  show  that  virulent  tubercle 
bacilli  may  be  found  in  the  sputum  on  sidewalks,  or  those  of 
Dixon  ^  to  demonstrate  that  they  may  be  swept  up  on  the 
skirts  of  ladies'  dresses. 

1  Preisich  and  Schiitz,  Berl.  khn.  Wchnschr.,  1902,  XXXIX,  466. 

2  Dieudonne,  Miinch.  med.  Wchnschr.,  1901,  XLVIII,  1439. 
»  Schumburg,  Ztschr.  f.  arztl.  Fortbild.,  Jena,  1905,  II,  567. 

*  Ostermann,  Ztschr.  f .  Hyg.  u.  Infectionskrankh.,  Leipz.,  1908,  LX,  375. 
s  Annett,  Thompson  Yates   Laboratory  Rep.,  1901-02,  IV,   Pt.  2, 
359. 

8  Higgins,  Pub.  Health,  Lond.,  1909-1910,  XXIII,  100. 
^  Letter  from  Dr.  Samuel  A.  Dixon  to  author. 


INFECTIOX  BY  COXTACT  15S 

In  Commimion  Cups.  —  Anders  ^  found  tubercle  bacilli  in 
ithe  aregs  from  communion  cups  in  a  Philadelphia  church,  and 
Moller^  from  the  communion  cup  of  a  sanatorium  chapel. 
Davison^  found  them  on  a  glass  used  for  some  weeks  in  a 
high  school.  He  also  demonstrated  pneumococci.  Klein* 
obtained  a  positive  tuberculous  reaction  once  after  inocula- 
tion of  the  swabbings  of  six  telephones,  although  on  twelve 
telephones  on  another  occasion^  he  was  unable  to  find  either 
diphtheria  or  tubercle  bacilli,  and  Hill*  was  unable  to  find 
either  bacillus  on  twenty-four  mouthpieces  of  lung-testing 
machines  in  Boston.  Huhs^  found  tubercle  bacilli  on  napkin 
rings  in  the  sanatorium  at  Stadtwald,  but  did  not  find  them 
on  the  spirometer  which  was  in  daily  use.  Price*  used  some 
water  in  which  sanatorium  dishes  had  been  washed  to 
inoculate  eight  guinea  pigs,  all  of  which  died  of  tuberculo- 
sis. Washings  from  dishes  which  had  been  first  washed  in 
the  ordinary  way  showed  no  bacilli. 

Contact  Chief  Mode  of  Infection.  —  Since  it  is  true  that 
pathogenic  organisms  begin  to  die  or  lose  their  virulence  when 
thrown  off  from  the  body,  we  are  forced  to  conclude  that  the 
closer  the  relationship  in  time  and  space  with  the  bearers  of 
the  germs,  the  greater  the  chance  of  infection.  Now  that 
the  number  of  unknown  foci  of  infection  and  the  oppor- 
tunities for  direct  transfer  of  secretions  have  been  demon- 
strated, the  deduction  is  certainly  permissible  that  contact 
infection  is  more  important  than  the  more  indirect  infection 
by  fomites  or  by  air. 

We  are  also  compelled  by  inductive  methods  to  place  the 
greatest  emphasis  upon  contact  infection.    In  the  chapter  on 

»  Anders,  J.  Am.  M.  As.s.,  Chicago,  1897,  XXIX,  789. 

'  Moller,  Deutsche  mod.  Wchnschr.,  1905,  XXXI,  548. 

'  Davison,  Tech.  World  Mag.,  Chicago,  1908,  IX,  623. 

*  Klein,  Lancet,  Lond.,  1908,  I,  1862. 

"  Ref.  J.  Am.  M.  A.s.s.,  1905,  XLIV,  1866. 

•  Hill,  Rep.  Bd.  Health,  Ho-ston,  1906,  91. 

'  Huh.s,  Zt.schr.  f.  Tuberk.  u.  Heil.stiittenw.,  I^ipz.,  1906,  IX,  396. 
'  Price,  Si-\tb  Internal.  Cong,  on  Tuberc,  Wash.,  1908,  I,  167. 


154         THE  SOURCES  AND  MODES  OF  INFECTION 

infection  by  fomites,  and  particularly  in  that  on  infection  by 
air,  much  evidence  is  presented  to  show  that  infection  usually 
does  not  take  place  unless  contact  is  fairly  close.  The  views 
here  presented  as  to  the  great  importance  of  contact  infec- 
tion, and  the  comparatively  slight  importance  of  air  infection 
and  fomites  infection,  gradually  developed  after  considera- 
tion of  much  experimental  and  epidemiological  evidence. 
The  two  facts  which  more  than  all  others  have  contributed 
to  these  views  have  been  the  restriction  of  scarlet  fever  and 
diphtheria  to  single  families  in  the  same  house,  and  the  suc- 
cess of  certain  hospitals  in  preventing  cross  infection,  when 
contact  infection  is  strictly  guarded  against. 

Disease  Spreads  in  Dwellings  only  by  Contact.  —  The 
rarity  with  which  scarlet  fever  and  diphtheria  pass  from 
one  family  to  another  in  the  same  house  has  already  been 
alluded  to,  but  it  is  worth  considering  again.  Of  4306  other 
families  in  Providence  living  in  the  same  house  with  a  case 
of  scarlet  fever,  only  295,  or  6.8  per  cent,  were  later  invaded 
by  the  disease.  This  includes  all  families,  whether  careful 
or  careless,  and  whether  or  not  the  initial  case  was  removed 
to  the  hospital;  but  as  less  than  10  per  cent  of  the  cases 
have  been  removed  to  the  hospital  during  the  23  years 
covered  by  the  figures,  hospital  isolation  can  have  been  of 
little  moment.  This  amount  of  infection  is  surprisingly  small, 
and  of  itself  indicates  very  strongly  that  close  and  intimate 
contact  is  usually  necessary  for  the  extension  of  this  disease. 
A  further  study  of  the  facts  indicates  this  still  more  clearly. 
During  the  last  5  years,  scarlet  fever  has  extended  to  118 
of  1888  other  families,  or  6.3  per  cent.  In  54,  or  22  per  cent, 
of  the  cases  infection  occurred  during  the  first  two  weeks,  of 
which  37  were  during  the  first  week.  Most  of  these  cases 
during  the  first  two  weeks  probably  derived  their  infection 
from  the  first  family  before  the  disease  was  recognized.  Only 
24  second  families  developed  their  infection  after  the  end  of 
the  second  week  and  while  the  warning  sign  was  on  the  house. 
This  is  the  time  when  the  patients  are  desquamating  and 


INFECTION  BY  CONTACT^  155 

when  the  disease  is  popularly  believed  to  be  most  infectious. 
These  24  cases  are  1.3  per  cent  of  the  1888  other  families  in 
the  infected  houses.  As  in  a  number  of  these  cases  there  was 
known  to  be  considerable  communication  between  the  fami- 
lies, it  seems  to  be  certain  that  in  an  ordinary  tenement 
house  scarlet  fever  is  not  readily  carried  from  one  family  to 
another,  and  that  effective  isolation  is  comparatively  easy. 
In  fact,  everything  goes  to  show  that  two  or  more  families 
may  live  in  the  same  house,  using  hallways,  doors,  and  even 
water-closets  in  common,  without  scarlet  fever  extending 
from  one  to  the  other.  All  that  is  necessary  is  that  there 
shall  be  absolutely  no  visiting  between  the  families,  and  that 
the  children  shall  never  meet  in  play.  I  do  not  know  that 
similar  data  have  been  collected  elsewhere,  but  Cameron^ 
has  shown  by  his  study  of  "return"  cases  of  this  disease 
that  in  many  instances  the  infecting  case  may  remain  in  the 
family  for  some  time,  providing  there  is  no  direct  contact 
with  the  well  persons. 

Diphtheria  is  as  little  likely  to  extend  from  family  to  family 
without  direct  contact  as  is  scarlet  fever.  During  the  last 
twenty-one  years,  in  Providence,  of  3667  other  families  living 
in  a  house  with  diphtheria,  only  263,  or  7.2  per  cent,  were 
invaded  by  the  disease.  During  the  five  years  1904  to  1908, 
of  1648  other  families,  114,  or  6.9  per  cent,  have  acquired  the 
disease.  Of  these,  only  38,  or  2.3  per  cent,  were  attacked  after 
the  first  week  of  the  initial  sickness  and  before  the  warning 
sign  was  removed.  As  was  shown  above,  many  of  these  infec- 
tions are  due  to  the  fact  that  the  first  case  is  not  recognized 
and  hence  the  different  families  in  the  house  continue  to  visit 
one  another;  or  in  some  instances  to  the  fact  that  persons  in 
the  second  family  carry  the  bacilli  for  a  time  without  being 
sick.  Probably  a  large  part  of  the  infections  during  the  first 
week  take  place  before  the  disease  is  recognized,  so  that  it 
seems  very  probable  that  less  than  2  and  perhaps  less  than 

1  Cameron,  Rep.  on  Return  Cases  of  Scarlet  Fever  and  Diphtheria, 
Lond.,  1901-02,  98. 


156         THE  SOURCES  AND  MODES  OF  INFECTION 

1  per  cent  of  families  living  in  a  house  with  a  case  of  diph- 
theria contract  the  disease  while  the  warning  sign  is  on  the 
house.  I  have  given  particular  attention  to  the  cases  of  diph- 
theria arising  in  other  families  in  the  house  while  the  warning 
sign  remained  on  the  apartment  where  the  disease  first  ap- 
peared, and  almost  always  there  is  known  to  be  direct  inter- 
course between  the  families.  Contact  infection,  then,  seems 
to  be  necessary  for  the  transfer  of  diphtheria  from  one  family 
to  another  living  in  different  apartments  of  the  same  house. 

Disease  spreads  in  Hospitals  only  by  Contact.  —  Another 
strong  reason  for  this  view  that  contact  infection  is  the  chief 
mode  of  extension  for  the  common  contagious  diseases  is  the 
success  of  certain  hospitals  in  preventing  cross  infection  by 
minimizing  in  every  way  the  opportunities  for  infection  by 
contact.  The  Parisian  hospitals,  particularly  the  Pasteur 
Hospital,  have  been  leaders  in  demonstrating  the  success  of 
this  method.  In  most  hospitals  for  contagious  diseases  great 
effort  is  made  to  prevent  cross  infection  by  separating  the 
different  diseases  to  a  considerable  distance,  since  the  theory 
prevails  that  air-borne  infection  is  the  chief  mode  of  spread. 
This  view  so  dominates  hospital  practice  that  numberless 
ways  escape  notice  by  which  disease  is  spread  by  very  direct 
contact,  with  the  result  that  in  most  hospitals  cases  of  cross 
infection  are  continually  developing. 

French  Hospitals.  —  The  French  seem  to  have  been  the 
first  to  appreciate  the  importance  of  guarding  against  contact 
infection,  and  an  interesting  account  of  the  efforts  made  is 
given  by  Grancher,^  who  was  one  of  the  pioneers.  Strict 
methods  of  "antisepsie  medicale,"  as  Grancher  calls  it,  were 
introduced,  and  it  was  found  possible  to  care  for  patients 
with  different  diseases  even  in  a  common  ward  with  far  less 
danger  of  transfer  than  before.  He  employed  wire  screens 
around  the  beds  to  impress  upon  the  nurses  the  necessity  for 
guarding  against  infection  by  contact.     During  the  years 

1  Grancher,  Cong.  Internat.  de  med.,  XIII.,  C.-r.  Par.,  1900,  Sec. 
de  med.  de  I'enfance,  478. 


INFECTION  BY  CONTACT  157 

1890  to  1900,  6541  patients  were  treated  in  Grancher's  wards, 
and  diphtheria  was  introduced  43  times,  but  only  once  did 
a  case  develop  in  the  wards.  Scarlet  fever  was  introduced 
19  times,  and  7  cases  developed  in  the  wards.  Less  suc- 
cess was  obtained  in  isolating  measles,  but  infections  were 
reduced  two-thirds.  Grancher  was  satisfied  that  even  this 
disease  was  spread  by  contact.  He  believed  that  in  clean 
wards  infection  is  rarely  air-borne;  it  is  "  objective,"  not 
"  atmospheric."  In  several  other  French  hospitals  the  impor- 
tance of  preventing  contact  infection  has  been  realized.  In 
some  of  them  isolation  is  made  easier  by  placing  the  patients 
in  separate  rooms  or  cubicles;  in  some,  partitions  are  placed 
between  the  beds.  These  partitions  may  be  full  height,  or 
may  stop  short  of  the  floor,  and  reach  only  just  above  the 
head.  Sometimes  screens  only  are  used.  In  1897  the  Min- 
turn  Hospital  in  New  York,  a  small  private  hospital,  was 
built  to  provide  isolation  in  separate  rooms  for  cases  of  scarlet 
fever  and  diphtheria.  But  the  most  notable  example  of  the 
new  method  is  the  Pasteur  Hospital  in  Paris,  opened  in  1900. 
The  success  of  these  various  hospitals  in  preventing  cross 
infection  is  correlated,  not  with  the  amount  of  isolation  as 
ordinarily  understood,  but  with  the  care  with  which  aseptic 
measures  are  carried  out  b}'  the  attendants.  The  cubicles, 
partitions  and  screens  certainly  cannot  prevent  infection  if 
the  nurses  without  taking  proper  precautions  pass  from  one 
case  to  another.  This  is  shown  by  the  constant  development 
of  cross  infection  in  the  ordinary  hospital.  It  was  in  the 
Pasteur  Hospital  that  the  principles  of  medical  asepsis  were 
first  fully  appreciated  and  carried  out  in  a  practical  manner. 
The  hospital  consists  of  two  pavilions  with  about  fifty  beds 
each,  designed  ostensibly,  one  pavilion  for  scarlet  fever  and 
one  for  diphtheria;  but,  as  is  shown  below,  all  sorts  of  cases 
are  admitted.  For  the  care  of  all  these  "  other  diseases  " 
and  mixed  and  doubtful  cases,  twelve  single  rooms  are  pro- 
vided in  each  ward,  all  opening  into  a  common  corridor,  the 
doors  of  which  are  usually  left  open.    The  same  nurses  look 


158        THE  SOURCES  AND  MODES  OF  INFECTION 

after  different  diseases,  often  in  adjoining  rooms.  The  disci- 
pline of  the  hospital  attempts  to  secure  an  entire  avoidance 
of  contact  infection,  and  is  remarkably  successful.  Yet  the 
procedures  are  all  very  simple.  The  nurse  always  sterilizes 
her  hands  after  waiting  on  the  patient;  she  wears  a  gown, 
which  is  kept  in  the  room,  when  anything  is  done  which 
would  be  likely  to  infect  her  clothing.  Nothing  goes  into  the 
room  except  what  is  sterile,  and  nothing  comes  out  without 
being  at  once  sterilized.  To  train  nurses  sufficiently  to  take 
charge  of  a  ward,  two  years  are  necessary,  but  the  nurses 
whom  I  saw  there  were  carrying  out  these  details  with  the 
same  precision  and  unconsciousness  which  are  shown  by  the 
bacteriologist  in  his  laboratory. 

English  Hospitals.  —  The  principles  of  aseptic  nursing  as 
applied  to  contagious  diseases  have  been  employed  in  a  num- 
ber of  places  in  England,  as,  for  instance,  in  the  North 
Eastern,  South  Western  and  London  Fever  hospitals  in 
London,  at  Walthamstow  and  Manchester,  and  doubtless  in 
other  places.  The  methods  adopted  in  the  Monsall  Hospital 
at  Manchester,  and  described  by  Gordon, ^  are  as  follows: 

"The  patient's  bed  in  the  general  ward  is  surrounded  with 
a  screen  covered  with  sheets,  which  are  kept  constantly  wet 
with  a  weak  solution  of  some  disinfectant.  The  main  pur- 
pose of  this  screen  is  to  serve  as  a  label,  and  to  remind  the 
nurses  that  certain  precautions  must  be  taken  for  the  patient 
behind  it.  At  the  same  time,  I  think  the  wet  sheets  may  pos- 
sibly arrest  infective  particles  that  are  projected  against  them 
in  the  acts  of  coughing  and  sneezing.  The  only  other  requi- 
sites are  two  glass  shelves  fixed  on  the  wall  behind  the  bed, 
and  a  locker  or  portable  cupboard  made  of  metal,  with  an 
enameled  surface,  which  can  easily  be  disinfected  and  kept 
clean. 

"  The  precautions  to  be  taken  by  the  nurses  in  attending 
patients  behind  this  screen  or  '  barrier '  are  printed  on  a 
card  fixed  to  the  screen,  and  are  as  follows: 

1  Gordon,  Rep.  on  Health  of  Manchester,  1908,  154 


INFECTION  BY  CONTACT  159 

Rules  in  Manchester.  —  "  Precautions  to  be  Observed  in 
the  Nursing  of  Barriered  Cases. 

"(1)  Rubber  gloves  are  to  be  worn  by  the  Nurse  for  all 
manipulations  connected  with  the  case,  including  the  han- 
dling of  clothes.  The  gloves  are  to  stand  in  a  bowl  of  1  in  400 
Izal  solution. 

"  (2)  The  following  utensils  are  to  be  marked  and  kept  on 
the  glass  shelves  or  in  the  locker  provided: 


Spatula 

Nozzles 

Clinical  Thermometer 

At  least  two  bowls. 

All  feeding  utensils  (plates,  spoons,  forks,  etc.). 


To  be  kept  completely 
immersed  in  a  1  to 
400  Izal  solution. 


"(.3)  A  plentiful  supply  of  wet  swabs,  with  a  bowl  contain- 
ing Izal  solution  to  receive  these  when  used,  is  to  be  kept  on 
the  locker.  Handkerchiefs  or  muslin  squares  are  not  to  be 
employed. 

"(4)  No  toys  or  books  that  have  once  been  used  inside 
the  barrier  are  to  be  taken  outside  it  except  to  be  destroyed. 

"  (5)  In  every  case  a  square  of  jaconette  is  to  be  placed  on 
the  pillow  slip,  and  over  this  a  piece  of  muslin;  the  latter  is 
to  be  renewed  whenever  soiled. 

"(6)  An  overall  is  to  be  worn  by  the  Nurse  whenever 
either  the  patient  or  the  clothes  are  handled.  This  is  to  be 
kept  inside  the  barrier." 

The  success  of  the  methods  described  in  the  preceding 
pages  is  well  shown  by  the  published  figures.  At  the 
Pasteur  Hospital  from  October  1,  1900,  to  April  19,  1903, 
the  following  cases  were  received: 

Diphtheria 443         Scarlet  fever 92 

Sore  throat 166         Erysipelas 163 

Smallpox 524  Phlegmon  of  tonsil. ...  28 

Chicken  pox 55         Other  diseases 219 

Measles 126  Mothers  with  infants. .  192 


160         THE  SOURCES  AND  MODES  OF  INFECTION 

Such  a  combination  furnishes  a  remarkably  fertile  field  for 
cross  infections.  During  the  next  year  about  750  cases  were 
admitted.^ 

During  this  whole  period  the  only  cases  which  developed 
in  the  hospital  were  5  of  smallpox,  2  of  erysipelas  and  1  of 
diphtheria.  Dr.  Loiseau  writes  me  that  since  1904  the  per- 
centage of  cross  infections  has  been  less  than  0.1  per  cent. 
At  the  Minturn  Hospital  in  New  York  there  has  been  no  in- 
stance of  infection  in  the  hospital.  At  the  Monsall  Hospital 
in  Manchester  in  1908  a  large  number  of  persons  admitted 
with  mistaken  diagnosis  were  cared  for  in  the  wards  by  the 
methods  described  without  contracting  the  disease,  and  a 
number  of  cases  of  mixed  infection  were  cared  for  in  the  open 
wards  without  infecting  others,  except  in  one  instance  when, 
owing  to  a  mistake  in  orders,  "  barrier  "  isolation  was  not 
promptly  instituted.  A  letter  just  received  from  Dr.  Arnold, 
who  has  succeeded  Dr.  Gordon  at  Monsall,  states  that  in 
order  that  the  patient  may  see  and  be  seen,  and  to  avoid 
the  dampness  of  the  wet  sheet,  he  has  substituted  a  tape 
which  as  effectually  prevents  the  mythical  aerial  flight  of  the 
germs,  or,  to  speak  literally,  equally  well  reminds  the  nurse 
that  she  must  be  clean. 

Is  Tuberculosis  Air-borne?  —  It  is  assumed  that  tuber- 
culosis, as  it  occurs  in  human  beings,  is  usually  an  air-borne 
disease,  and  as  will  be  shown  on  another  page,  there  is  more 
reason  for  such  an  assumption  concerning  this  than  concern- 
ing most  diseases.  Yet  there  is  in  certain  quarters  a  growing 
tendency  to  attribute  to  contact  infection  more  importance 
than  formerly.  Yet  it  must  be  confessed  that  most  writers 
on  this  disease  lay  no  emphasis  on  contact  infection,  and 
some  scarcely  mention  it.  Cornet,^  in  speaking  of  kissing, 
the  most  direct  means  of  contact  infection,  says  that  it  is 
incredible  that  tuberculosis  should  be  transmitted  in  this 
way,  for  the  saliva  is  ordinarily  germ  free,  and  the  germs  if 

1  Martin,  Bull,  med.,  Par.,  1904,  XVIII,  251. 

2  Cornet,  Nothnagel's  Encyclopedia,  Tuberculosis,  187. 


INFECTION  BY  CONTACT  161 

present  would  not  be  carried  to  the  lungs.  Cornet's  first 
contention  is  certainly  not  correct,  for  Neild  and  Dunkley,  as 
before  mentioned,  found  tubercle  bacilli  on  the  tip  of  the 
tongue  of  phthisical  patients  examined  during  intervals  of 
freedom  from  cough.  They  also  report  cases  of  lupus,  due  in 
all  probability  to  inoculation  with  saliva,  and  refer  to  others 
reported  by  Wild.^ 

There  has  been  little  experimental  work  to  determine  the 
part  played  by  contact  infection  in  tuberculosis.  The  work 
of  Bartel  and  Spieler"  indicates  that  guinea  pigs  exposed 
under  natural  conditions  to  contact  with  the  members  of  a 
tuberculous  family  more  often  develop  the  disease  than  do 
animals  exposed  merely  to  the  air  of  the  room,  while  the 
experiments  of  Packard,  though  inconclusive,  indicate  little 
difference. 

Infection  by  Alimentary  Tract.  —  There  seems  to  be  evi- 
dence that  the  tonsils  may  be  the  seat  of  infection  in  many 
cases  of  tuberculosis.  Harbitz^  has  very  forcibly  called  atten- 
tion to  the  probability  that  tubercle  bacilli  frequently  gain 
access  to  the  body  through  the  tonsils.  He  examined  the 
tonsils  and  lymphatic  glands  of  a  large  number  of  children, 
and  found  latent  tuberculosis  in  many  of  the  tonsils,  and 
latent  bacilli  in  the  cervical  glands  in  17  instances,  much  more 
often  than  in  the  mesenteric  glands.  He  thinks  that  a  more 
careful  study  of  the  tonsils  and  lymph  nodes  would  reveal 
much  latent  tuberculous  infection,  and  he  thinks  that  a  con- 
siderable amount  of  infection  takes  place  through  the  tonsils. 
Harbitz  mentions  Grawitz,^  Aufrecht'^  and  Beckmann  as  sup- 
porting this  view.  Ravenel  and  Reichel"  review  much  litera- 
ture, and  refer  to  Wood's  experimental  infection  of  swine 

'  Wild,  Brit.  M.  J.,  1899,  II,  13.53. 

^  Referred  to  in  the  chapter  on  infection  ijy  air. 

>  Harbitz,  J.  Infect.  Dis.,  Chicago,  1905,  11,  143,  and  especially  198. 

*  Grawitz,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  711. 

»  Aufrecht,  Verhandl.  d.  deutsch.  path.  Gesellsch.,  Berl.,  1901-02, 
IV,  6.5. 

"  Ravenel  and  Reichel,  J.  Med.  Research,  Boat.,  1908,  XVIII,  1. 


162         THE  SOURCES  AND  MODES  OF  INFECTION 

through  the  tonsils,  the  course  of  the  bacilli  being  apparently 
through  the  submaxillary  and  cervical  glands.  Benome  ^ 
caused  infection  in  animals  through  the  mouth  and  pharynx. 
Bandeher'  finds  primary  tuberculosis  of  the  tonsils  not  so  rare 
as  is  generally  believed,  but  he  does  not  consider  the  tonsils 
as  a  frequent  starting  point  of  phthisis.  Mohler  and  Ravenel 
from  experiments  and  observations  consider  the  mouth  as 
a  frequent  site  of  infection  in  the  tuberculosis  of  hogs. 

Contact  Infection  in  Tuberculosis.  —  The  nose  also  may 
be  the  seat  of  infection.  Cornet,^  by  applying  infective  ma- 
terial by  means  of  a  feather  to  the  nasal  mucous  membrane 
of  guinea  pigs,  was  able  to  produce  disease  of  the  nose  and 
submaxillary  glands.  Renshaw  *  was  able  in  the  same  way 
to  infect  seven  of  eight  animals.  As  tubercle  bacilli  are  nu- 
merous upon  the  hands  of  consumptives  and  upon  various 
articles  used  by  them,  it  is  evident  that  fresh  bacilli  must  be 
frequently  carried  to  the  mouth  and  nose  of  persons  near  by, 
and  may  either  infect  directly  through  the  mouth,  nose  and 
pharynx,  or  may  be  swallowed  and  enter  the  circulation 
through  the  lower  part  of  the  alimentary  canal.  The  only 
question  is,  How  frequently  does  this  happen?  As  was  stated 
above,  it  is  the  opinion  of  many  that  it  is  a  very  common 
mode  of  infection.  Moore ^  is  of  the  opinion  that  in  cat- 
tle tuberculosis  is  spread  chiefly  by  the  animals  licking 
one  another,  and  b}^  their  eating  and  drinking  from  the 
same  vessels.  Bartel^  believes  that  infection  by  pharynx, 
stomach  and  intestines  is  more  common  than  has  been  sup- 
posed, in  which  view  he  supports  Weichselbaum,^  Volland,'' 

'  Benome,  Ref.  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  888. 
^  Bandelier,  Beit.  z.  Klin.  d.  Tuberk.,  Wiirzb.,  1906,  VI,  1. 
^  Cornet,  Nothnagel's  Encyclopedia,  Tuberculosis,  154. 
^  Renshaw,  J.  Path,  and  Bacteriol.,  Lond.,  1901,  VII,  142. 
5  Moore,  Conference  of  Sanitary  Officials,  N.  Y.,  1907,  37. 
"  Bartel,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  95. 
^  Weichselbaum,   Festsch.  VI    Konf.    Internat.  Tuberk.,    Wien    u. 
Leipz.,  1907. 

*  Volland,  Berl.  klin.  Wchnschr.,  1899,  XXXVI,  1031. 


INFECTION  BY  CONTACT  163 

Kavacs^  and  Preisich  and  Schiitz.^  Among  others  who  at- 
tribute much  importance  to  contact  infection  may  be  men- 
tioned Wassermann/  Calmette  and  Landouzy.* 

Certainly  the  opportunities  for  the  direct  transfer  of  fresh 
moist  infective  material  in  the  home  of  a  phthisical  patient 
must  be  very  great,  while  the  chance  of  the  infective  material 
becoming  dried,  pulverized  and,  while  still  virulent,  being  car- 
ried to  the  pulmonary  alveoli,  must  be  comparatively  small. 
Unless  there  is  some  good  reason  to  think  otherwise,  one 
would  naturally  attribute  to  contact  infection  the  chief  role 
in  the  extension  of  this  disease,  at  least  in  the  family.  The 
only  objection  is  offered  by  the  pathologists,  many  if  not 
most  of  whom  affirm  that  the  evidence  points  to  direct  infec- 
tion of  the  lungs  by  the  inspired  air.  There  are,  however, 
many  able  experimenters  who  think  otherwise,  and  who  main- 
tain that  tubercle  bacilli  may  enter  the  body  at  various  points 
and  reach  the  lungs  through  the  lymph  channels.  It  is  impos- 
sible for  the  writer  properly  to  weigh  pathological  evidence, 
but  that  the  question  is  still  sub  judice  must  be  admitted. 
Under  the  circumstances  it  seems  to  be  wise  to  assume 
as  a  working  hypothesis  that  contact  infection  is  a  factor  of 
great  importance  in  the  causation  of  human  tuberculosis.  It 
is  certainly  essential  to  guard  against  such  infection  in  every 
way,  and  from  a  person  who  does  thus  conduct  himself  in  a 
cleanly  manner  at  all  times,  diffusion  of  the  disease  through 
the  air  would  be  impossible.  Undue  emphasis  laid  upon  the 
invisible  and  therefore  terrifying  infection  in  the  air  has  done 
more  than  anything  else  to  develop  the  unfortunate  phthisi- 
phobia  which  so  often  renders  miseraljle  the  life  of  the  tuber- 
culous, and  seriously  interferes  with  rational  measures  for  the 
restriction  of  the  disease. 

'  Kavacs,  Zciglers  BoitraRo  zur.  Path.  Anat.,  1906,  XL. 
2  Preisich  and  Schutz,  Hcrl.  khn.  W.schn.schr.,  1902,  XXXIX,  466. 
'  Wasscrmann,  Bcrl.  klin.  Wchnschr.,  1908,  Nr.  48. 
*  Calmette  and  Landouzy,  Si.xth  Internat.  Cong,  on  Tuberc,  Waah., 
1908,  I,  110. 


164         THE  SOURCES  AND  MODES  OF  INFECTION 

Importance  of  Contact  Infection.  —  I  have  sometimes  been 
told  that  I  lay  too  much  emphasis  on  contact  infection,  but 
if  it  is  the  principal  way  in  which  disease  spreads,  too  much 
emphasis  cannot  be  placed  upon  it,  and  it  seems  to  me  that 
the  evidence  is  that  it  is  the  chief  mode  of  infection.  Even 
if  it  is  not  so  important  as  is  here  alleged,  every  one  must 
admit  that  it  is  of  considerable  importance,  yet  until  recently 
very  little  attention  has  been  paid  to  it.  If  contact  infection 
is  the  chief  mode  of  extension  of  the  contagious  diseases,  then 
defense  against  them  becomes  more  largely  a  personal  affair 
than  we  have  been  taught.  We  do  not  have  to  rely  exclu- 
sively on  the  municipality  for  our  protection,  awaiting  forced 
isolation,  hospital  construction,  disinfection  and  the  like,  but 
can  largely  protect  ourselves  by  keeping  our  fingers  out  of 
our  mouths,  and  also  everything  else  except  what  belongs 
there.  It  may  not  be  possible  to  prevent  all  contagious  sick- 
ness in  this  way,  but  some  can  be  avoided,  and  perhaps  most 
of  it.  Contact  infection  is  avoided  by  personal  cleanliness, 
and  personal  cleanliness  is  demanded  by  decency,  good  man- 
ners and  refinement,  as  well  as  by  hygiene.  It  is  not  much 
trouble  to  be  decently  clean,  and  it  is  not  very  expensive. 
It  is  a  serious  mistake  to  build  an  expensive  isolation  hos- 
pital that  does  not  check  disease,  or  to  construct  a  filter  when 
it  is  not  needed ;  but  no  harm  would  be  done  if  the  views  here 
presented  should  be  found  to  be  erroneous  and  people  should 
learn  to  wash  their  hands  and  keep  their  fingers  out  of  their 
mouths  to  no  purpose  so  far  as  disease  prevention  is  concerned. 
It  seems  certain  that  much  can  be  done  to  prevent  the  spread 
of  disease  in  the  family  and  in  hospitals,  schools  and  institu- 
tions, if  only  personal  cleanliness  be  insisted  upon.  Yet  such 
cleanliness  or  medical  asepsis  is  sadly  neglected  by  physicians 
as  well  as  by  nurses.  Rather  strong  preaching  is  needed 
when,  as  was  referred  to  on  another  page,  a  typhoid  nurse  is 
detailed  for  the  double  duty  of  washing  bedpans  and  preparing 
food.  It  is  certainly  necessary  to  insist  somewhat  strenuously 
on  reform  when  such  occurrences  as  the  following  take  place. 


IXFECTIOX  BY  COX  TACT  165 

Disregard  of  Contact  Infection. —  Thus,  at  one  of  the  finest 
hospitals  in  this  country,  with  separate  wards  for  scarlet  fever 
and  diphtheria,  a  considerable  number  of  cases  have  arisen 
in  the  general  wards.  The  germs  were  supposed  to  be  air- 
borne, as  it  was  said  there  was  no  other  possible  avenue  of 
infection.  When  I  saw  the  head  nurse  lick  her  finger  to 
facilitate  turning  the  bedside  charts  of  diphtheria  patients,  I 
suspected  that  the  principles  of  medical  asepsis  had  not  been 
entirely  mastered.  Called  to  see  a  case  of  scarlet  fever  in  a 
well-to-do  family,  I  found  the  door  of  the  sick-room  carefully 
hung  with  a  sheet  to  keep  the  infection  from  the  other  chil- 
dren. After  examining  the  throat  with  a  spatula  I  handed 
the  latter  to  the  mother.  She  took  it  into  the  hall  and  put 
it  on  an  upholstered  sofa,  and  with  her  saliva-infected  hands 
opened  the  door  of  an  adjoining  room.  The  attending  physi- 
cian meanwhile  sat  on  the  bed  and  handled  the  patient,  an 
entirely  unnecessary  proceechng  at  that  time,  and  except  for 
the  example  set  him,  would  have  forgotten  to  wash  his  hands 
before  leaving.  A  certain  hospital  determined  to  cop3'  in  one 
of  its  wards  the  cubicle  system  of  the  French,  but  had  so 
missed  its  essential  features  that  I  found  doctors  and  nurses 
going  from  cubicle  to  cubicle  feeling  the  pulse,  smoothing  the 
bedclothes,  and  handling  dishes  without  even  stopping  to 
wash  their  hands.  Meanwhile  the  screen  was  supposed  to 
prevent  the  microbes  from  passing  from  bed  to  bed,  and  we 
all  carefully  wore  gowns  and  caps  so  that  the  wicked  little 
germ  might  not  jump  into  our  hair  and  then  jump  off  again 
onto  the  next  patient.  In  another  fine  hospital  for  conta- 
gious disea-ses,  where  great  stress  is  laid  upon  ample  space 
between  different  diseases  so  as  to  prevent  cross  infection, 
the  superintendent  was  observed  freely  to  touch  articles  about 
the  ward,  and  handle  the  patients,  and  then  go  to  the  public 
office  without  even  washing  his  hands.  Such  incidents  could 
be  multiplied  indefinitely.  The  superintendent  of  another  hos- 
pital invited  another  visitor  and  myself  to  eat  ice  cream  from 
the  same  spoon  as  himself,  which  spoon  was  then  replaced 


166         THE  SOURCES  AND  MODES  OF  INFECTION 

in  the  freezer  which  was  to  supply  the  wards.  I  was  most 
of  all  impressed  with  the  fact  that  at  the  International  Con- 
gress on  Tuberculosis  in  1908  a  large  number  of  the  readers 
of  papers  moistened  their  fingers  with  their  tongue  when  turn- 
ing the  pages,  and  in  each  of  the  sections  only  one  drinking 
glass  was  provided  for  all  the  speakers;  and  this  continued 
without  protest  for  a  day  or  two.  If  the  most  distinguished 
investigators  and  health  officials  of  the  world,  gathered  to 
study  the  most  important  contagious  disease,  show  no  appre- 
ciation whatever  of  the  importance  of  contact  infection,  it 
is  certainly  time  for  some  one  to  be  emphatic. 

Personal  Prophylaxis.  —  The  discovery  that  disease  germs 
are  rarely  able  to  maintain  themselves  outside  of  the  body 
clouded  the  hopes  of  those  who  expected  by  municipal  house 
cleaning  to  "  stamp  out  the  zymotic  diseases,"  and  the  later 
discovery  of  numerous  missed  cases  and  carriers  has  shown 
that  isolation  of  the  sick  controls  infection  far  less  than  was 
believed.  These  somewhat  discouraging  facts  are  to  a  large 
degree  offset  by  what  has  been  learned  of  the  modes  of 
infection.  Formerly  air  infection  was  chiefly  feared;  now  it 
appears  that  contact  infection  is  of  prime  importance.  For- 
merly dependence  was  placed  upon  the  state  to  isolate  and 
disinfect;  now  it  appears  that  the  individual  can  protect  him- 
self, and  as  easily  protect  others  if  he  chance  to  be  infected. 
It  is  usually  comparatively  simple  so  to  live  as  not  to  allow 
the  secretions  of  others  to  come  in  contact  with  one's  own 
mucous  surfaces,  and  it  is  easy,  and  should  be  considered 
immoral,  to  allow  one's  own  secretions  to  be  so  placed  that 
they  may  infect  another.  Personal  cleanliness  is  less  expen- 
sive than  municipal  cleanliness,  and  is  within  the  reach  of  all. 

Need  of  Education.  —  When  one  notes  the  utter  disregard 
of  medical  asepsis  shown  in  our  hospitals  and  medical  con- 
gresses, one  is  apt  to  feel  that  the  education  of  the  public  in 
habits  of  personal  cleanliness  will  take  a  very  long  time;  but 
some  encouragement  is  felt  when  it  is  remembered  that  it  is 
not  so  very  long  ago  that  excrement  was  commonly  thrown 


INFECTION  BY  CONTACT  167 

into  the  street  and  garbage  was  tossed  under  the  tables  of 
the  great.  It  is  only  a  few  years  since  our  sidewalks  were 
flecked  with  saliva,  but  now  nineteen  persons  out  of  twenty 
are  ashamed  to  be  caught  spitting  on  the  pavement.  Perhaps 
we  may  all  soon  learn  to  stop  distributing  our  secretions  so 
freely  among  our  friends. 

Education  in  School.  —  As  the  avoidance  of  contact  infec- 
tion is  chiefl}^  a  personal  matter,  the  present  need  is  for  educa- 
tion. First  of  all,  the  teachers  in  the  medical  schools  and  the 
staffs  of  hospitals  must  learn  to  appreciate  the  importance  of 
this  mode  of  infection.  It  is  not  unreasonable  to  hope  that 
in  a  few  years  the  schools  and  the  hospitals  will  place  as 
much  emphasis  on  medical  asepsis  as  they  now  do  on  surgical 
asepsis,  and  it  is  to  these  centers  that  we  must  look  for  the 
education  of  physicians,  health  officers  and  nurses.  To  edu- 
cate the  general  public  is  a  more  difficult  matter.  Some  years 
ago  Dr.  Theobald  Smith  called  my  attention  to  the  desirabil- 
ity of  teaching  school  children  something  about  the  require- 
ments of  personal  cleanliness,  and  since  then  I  have  each  year 
distributed  to  each  school  child  the  following  "  dont's  " 

REMEMBER    THESE    THINGS. 

Do  not  spit  if  you  can  help  it.  Never  spit  on  a  slate,  floor, 
or  sidewalk. 

Do  not  put  the  fingers  into  the  mouth. 

Do  not  pick  the  nose  or  wipe  the  nose  on  the  hand  or  sleeve. 

Do  not  wet  the  finger  in  the  mouth  when  turning  the  leaves 
of  books. 

Do  not  put  pencils  into  the  mouth  or  wet  them  with  the 
lips. 

Do  not  put  money  into  the  mouth. 

Do  not  put  pins  into  the  mouth. 

Do  not  put  anything  into  the  mouth  except  food  and  drink. 

Do  not  swap  apple  cores,  candy,  chewing  gum,  half-eaten 
food,  whistles  or  bean  blowers,  or  anything  that  is  put  into 
the  mouth. 


168        THE  SOURCES  AND  MODES  OF  INFECTION 

Never  cough  or  sneeze  in  a  person's  face.  Turn  your  face 
to  one  side. 

Keep  your  face  and  hands  clean;  wash  the  hands  with  soap 
and  water  before  each  meal. 

Providence,  May,  1901. 

An  explanatory  circular  is  sent  to  the  teachers,  and  of  late 
a  short  account  of  the  sanitarj^  reasons  for  personal  cleanli- 
ness has  been  distributed  to  children  above  the  primary 
grade.  Large  printed  copies  of  the  "  dont's  "  have  been 
framed  and  hung  in  the  schoolhouses. 

Much  kindergarten  work  is  of  such  a  nature  as  to  inculcate 
rather  than  discourage  cleanly  habits.  Children  work  in  com- 
mon in  moist  clay  and  sand,  use  the  same  "gifts"  and  toys 
and  are  brought  into  close  contact  in  the  games.  Miss  Bessie 
M.  Scholfield,  the  supervisor  of  these  schools  in  Providence,  is 
now  attempting,  without  any  undue  expense  or  violent  change 
of  methods,  to  employ  kindergarten  work  as  a  means  of  teach- 
ing some  of  the  principles  of  personal  hygiene. 

Municipality  should  encourage  Cleanliness.  —  Besides 
efforts  that  are  directly  educational  the  municipality  can  do 
much  indirectly  to  encourage  habits  of  personal  cleanliness 
and  to  prevent  the  distribution  of  the  secretions  and  excre- 
tions of  the  body.  The  common  drinking  cup  is  a  most 
efficient  means  of  such  distribution,  and  it  should  be  abolished 
in  all  schools  and  other  public  institutions.  This  has  been 
done  in  many  places,  and  individual  cups  or  specially  designed 
drinking  fountains  substituted.  The  example  is  now  being 
followed  by  some  railways,  factories  and  shops.  The  states 
of  Kansas,  Michigan  and  Mississippi  have  forbidden  the 
use  of  a  common  drinking  glass  on  railways,  and  the  Lacka- 
wanna and  some  other  roads  advertise  as  an  attraction  free 
cups  of  paraffin  paper  for  each  passenger.^  Hundreds  of 
churches  have  adopted  the  individual  communion  cup.  The 
roller  towel  should  go  the  way  of  the  common  drinking  cup. 
»  J.  of  Outdoor  Life,  1909,  VI,  371. 


IXFECTIOX  BY  CONTACT  169 

People  are  more  likely  to  keep  clean  if  it  is  easy  to  do  so. 
Hence  the  establishment  of  public  baths  may  be  considered 
a  real  sanitary  measure.  While  compulsion  can  have  little 
share  in  the  campaign  for  cleanliness,  certain  prohibitions  are 
entirely  reasonable  and  feasible.  Thus  ordinances  against 
spitting  on  the  sidewalks  and  the  floors  of  public  places  have 
done  much  to  teach  people  to  take  proper  care  of  their  secre- 
tions. Reference  has  already  been  made  to  evidence  that  the 
abolition  of  privy  vaults  results  in  a  decrease  in  typhoid  fever. 
Privy  vaults  certainly  encourage  the  improper  disposal  of 
excreta  and  general  uncleanly  habits.  A  good  sewage  system 
and  the  removal  of  vaults  and  cesspools  do  much  to  prevent 
contact  infection,  at  least  in  the  fecal-borne  diseases. 


CHAPTER  V. 

INFECTION    BY    FOMITES. 

Definition  of  Term.  —  As  was  shown  in  the  preceding 
chapter,  it  seems  very  probable  that  contagious  disease  may 
often  be  caused  by  the  quite  direct  transference  of  the  germs 
from  one  person  to  another  on  such  objects  as  cups,  pencils, 
pipes,  the  fingers,  etc.  This  mode  of  transference  should 
properly  be  considered  a  form  of  contact  infection.  The  term 
contact  infection,  as  commonly  used  at  the  present  time,  does 
not  necessarily  imply  the  immediate  touching  of  two  persons, 
but  it  does  imply  the  comparatively  direct  transference  of 
quite  fresh  material  from  one  to  another.  Although  almost 
any  object  may  in  this  manner  be  the  bearer  of  infection,  it 
would  not  ordinarily  be  considered  as  fomites.  By  fomites 
are  usually  meant  infected  objects  which  retain  the  infection 
for  some  time.  A  toy  used  by  a  diphtheria  patient  and  sent 
to  a  distant  town  and  there  giving  rise  to  the  disease,  the 
dress  of  a  scarlet-fever  patient  put  away  for  weeks  or  months 
and  brought  out  only  to  cause  another  case,  a  library  book 
carrying  the  infection  of  smallpox  from  one  household  to 
another,  blankets  loaded  with  typhoid  bacilli  in  South  Africa 
transferring  infection  to  England,  infected  hides  from  Asia 
causing  anthrax  in  Philadelphia,  blank  cartridges  as  the  bear- 
ers of  tetanus  germs,  and  the  various  objects  in  a  room  lately 
occupied  by  a  case  of  any  contagious  disease  giving  rise  to 
the  same  affection  in  newcomers,  would  all  be  recognized  as 
fomites.  The  cup  which  carries  the  moist  saliva  from  one 
school  child  to  another,  the  borrowed  pencil  which  transfers  the 
fresh  syphilitic  virus  from  lip  to  lip,  and  the  urine-moistened 
closet  seat  which  infects  the  fingers  and  then  the  mouth  of 
the  next  user,  are  not  thought  of  as  fomites  but  as  the  neces- 

170 


INFECTION  BY  FOMITES  171 

sary  media  for  that  intimate  mode  of  disease  transference 
which  is  coming  to  be  called  contact  infection.  This  dis- 
tinction between  the  two  classes  of  bearers  of  infection  is 
somewhat  arbitrar}'^,  and  not  very  definite,  but  is  eminently 
practical.  In  this  book,  by  infection  by  fomites  is  meant  a 
transference  of  infecting  material  on  objects  under  such  con- 
ditions that  considerable  time  elapses,  days  at  least,  usually 
weeks,  sometimes  months. 

Yellow  Fever  and  Fomites.  —  If  one  takes  up  the  older 
text-books  on  yellow  fever  it  will  be  found  that  fomites  were 
considered  the  most  important  means  in  the  extension  of  this 
disease.  The  invasion  of  cities  and  countries  was  usually 
attributed  to  this  mode  of  carriage.  This  was  the  general 
view  up  to,  and  indeed  after,  the  discovery  of  the  role  played 
by  the  mosquito,  and  numerous  instances  of  such  transference 
are  given.  Thus  the  federal  inspectors^  attributed  the  out- 
break at  Brunswick,  Ga.,  to  ballast  brought  from  Cuba.  The 
disease  was  supposed  to  have  been  carried  from  New  Orleans 
to  Havana  by  means  of  second-hand  oyster  buckets.'  Lice- 
aga'  gives  instances  of  the  transmission  of  yellow  fever  by 
a  shipload  of  grain  from  New  Orleans,,  by  cloth  spread  out 
on  the  grass  to  dry,  by  general  merchandise,  by  bagging,  by 
clothing,  and  by  ballast.  Horlbeck*  says  that  two  persons 
at  Key  West  contracted  yellow  fever  from  sleeping  on  a  mat- 
tress that  was  brought  from  Cuba. 

Never  so  Transmitted.  —  In  all  these  instances  the  evi- 
dence is  the  same:  a  locality  has  long  been  free  from  yellow 
fever,  something  is  imported  from  an  infected  place  and  the 
disease  develops.  What  could  be  clearer?  The  proofs  that 
it  is  a  fomites-ljorne  disease  were  far  more  numerous  and 
stronger  for  yellow  fever  than  for  almost  any  other  disease. 

>  Rep.  Surg.  Gen.  U.  S.  Mar.  Hosp.  Serv.,  1893,  II,  33. 

*  Report  on  Shipment  of  Merchandise,  U.  S.  Mar.  Hosp.  Serv., 
Special  Report,  ISOn,  9. 

'  Lireaga,  Am.  Piih.  Health  Ass.  Rep.,  1898,  XXIV,  122. 

*  Horlbeck,  Am.  Pub.  Health  Ass.  Rep.,  1897,  XXIII,  436. 


172         THE  SOURCES  AXD  MODES  OF  INFECTION 

Yet  we  now  know  that  yellow  fever  never  was,  nor  could  be, 
transmitted  in  any  such  way.  Such  a  mistake,  a  mistake  which 
cost  millions  upon  millions  because  of  the  needless  interrup- 
tion of  commerce,  and  disinfection,  should  make  us  careful 
how  on  similar,  but  weaker,  evidence  we  attribute  importance 
to  fomites  as  a  means  of  infection  in  other  diseases,  and  should 
lead  us  to  inquire  what  proof  there  is  that  the  long  persist- 
ence of  infection  on  things  is  a  weighty  factor  in  the  trans- 
mission of  disease. 

Smallpox.  —  It  does  not  require  much  search  in  medical 
literature  to  find  numerous  instances  of  the  alleged  trans- 
mission of  disease  by  fomites.  Recent  text-books  and  jour- 
nals are  full  of  them.  Welch  and  Schamberg^  state  that 
smallpox  was  brought  to  Philadelphia  on  cotton  from  the 
South,  but  the  only  reasons  for  thinking  so  were  that  there 
was  much  smallpox  in  the  cotton  region  and  none  in  Phila- 
delphia, and  that  the  patient  handled  cotton.  Not  long  since 
the  health  officer  of  a  western  city  reported  that  the  principal 
source  of  smallpox  in  that  city  was  lumber,  his  assumption 
being  based  on  the  facts  that  there  was  much  of  the  disease 
in  the  lumber  camps,  that  the  rough  lumber  was  well  fitted 
to  carry  contagion,  and  that  in  most  families  the  first  person 
attacked  was  engaged  in  some  sort  of  woodworking.  The 
above  are  fair  samples  of  the  kind  of  evidence  on  which  the 
theory  of  fomites  infection  rests.  Smith  ^  reports  that  a  man 
from  Paris  died  in  London  of  what  was  probably  malignant 
smallpox.  Two  people  who  afterwards  slept  in  the  same  bed, 
on  different  days,  developed  the  disease,  as  did  the  girl  who 
sorted  at  the  laundry  the  soiled  linen  from  this  hotel. 

Scarlet  Fever.  —  A  recent  writer  in  Public  Health  ^  reports 
six  instances  of  house  infection  giving  rise  to  scarlet  fever, 
in  one  case  nine  months  after  the  first  patient  was  sick.    The 

'  Welch  and  Schamberg,  The  Acute  Infectious  Diseases,  Phila.,  1905, 
160. 

2  Smith,  Pub.  Health,  Lond.,  1901-02,  XIV,  211. 

3  Trotter,  Pub.  Health,  Lond.,  1906-07,  XIX,  745. 


INFECTIOX  BY  FOMITES  173 

only  evidence  was  the  recurrence  of  the  disease  in  the  house, 
Welch  and  Schamberg^  quote  from  others  reports  of  fomites 
infection  in  this  disease.  Boeck  states  that  the  hair  of  a 
scarlet-fever  patient  caused  the  disease  twenty  years  after. 
Another  physician  caught  the  disease  from  a  coat  which  he 
wore  while  attending  a  case  a  year  and  a  half  before.  The 
health  officer  of  Detroit^  reports  two  cases  due  to  infection 
from  books  which  had  been  used  by  a  patient  some  months 
before.  Wende'  states  that  quilts  used  by  scarlet-fever 
patients  in  August,  and  put  away  without  disinfection, 
caused  the  disease  in  November.  The  reports  of  the  state 
board  of  health  of  Michigan^  give  instances  of  the  per- 
sistence of  the  scarlet-fever  virus  for  years  in  houses,  letters, 
books,  etc. 

Diphtheria.  —  Buckley^  quoted  from  the  Newton,  Vic- 
toria, Health  Report  an  instance  where  a  cornet  used  by  a 
diphtheria  patient  was  put  away  for  four  years,  and  was  then 
found  by  some  children,  who  contracted  the  disease  from  it. 
He  gives  another  instance  where  the  disease  recurred  in  the 
house  after  a  period  of  two  years.  At  a  time  when  Manila 
was  absolutely  free  from  diphtheria,  an  American  child  who 
had  been  there  over  a  year  received  some  Christmas  presents 
from  St.  Louis,  and  was  taken  sick  a  few  days  later.  Chris- 
tian" writes  of  the  transmission  of  diphtheria  on  carpenters' 
tools  which  were  sent  from  one  shop  to  another. 

Cholera.  —  A  number  of  instances  of  the  transmission  of 
cholera  by  soiled  clothing  are  given  in  the  Report  of  the 
Marino  Hospital  Service  for  1893.'  In  nearly  every  instance 
the  clothing  was  brought  from  foreign  countries.     Because 

*  Welch  and  Schamberg,  The  Acute  Infectious  Diseases,  Pliila.,  1905, 
344. 

«  Rep.  B(l.  of  Health,  Detroit,  for  year  ending  June  30,  1903,  11. 
'  MufTalo  San.  Bull  ,  Nov   .30,  1908. 

♦  Rep.  St    Hd.  Health,  Mich.,  1900,  1.34;  1907,  133. 
"  Pill)    Health,  Lotid.,  1900-07,  XIX,  29G. 

•  Bull.  N.  Y.  St.  Boanl  of  Health,  .June,  1907,  r,. 

'  Rep.  Surg.  Gen.  U.  S.  Mar.  Hosp.  Serv.,  1893,  Vol.  II,  353. 


174         THE  SOURCES  AXD  MODES  OF  INFECTION 

a  company  of  soldiers  had  suffered  from  typhoid  fever  for 
two  years,  and  the  disease  ceased  on  disinfecting  the  bar- 
racks, the  outbreak  was  believed  to  have  been  due  to  room 
infection.^ 

Before  weighing  the  value  of  this  evidence  it  is  perhaps 
worth  while  to  consider  some  of  the  things  which  are  most 
often  alleged  to  serve  as  fomites. 

Infected  Clothing.  —  From  the  time  when  the  priest  was 
directed  how  to  detect  leprosy  in  woolen  and  linen^  to  the 
present,  clothing  has  been  considered  an  important  vehicle 
of  infection.  It  is  not  to  be  doubted  that  disease  germs  may 
be  carried  on  clothing.  If  clothing  is  soiled  with  a  consider- 
able quantity  of  infected  saliva,  feces,  urine  or  pus,  and  if 
while  fresh,  say  within  a  few  hours  or  days,  it  is  brought  in 
contact  with  susceptible  persons,  disease  may  result.  If  it  is 
folded  and  put  away  in  the  dark,  especially  if  it  be  in  a  damp 
place,  it  may  remain  infectious  perhaps  for  months.  But  as 
bacteria  as  a  rule  die  rapidly,  and  as  there  must  be  a  sequence 
of  gross  infection,  favorable  conditions  for  survival,  and  con- 
tact with  susceptible  persons,  it  does  not  seem  likely  that 
disease  is  often  caused  in  this  way. 

Many  instances  are  recorded,  usually  only  of  possible,  rarely 
of  probable,  transference  of  disease  by  clothing.  Of  yellow 
fever  more  than  of  any  other  disease  has  this  been  alleged,  yet 
we  now  know  that  such  transmission  of  this  disease  is  impos- 
sible. Many  writers  also  report  the  spread  of  bubonic  plague 
by  means  of  clothing,  but,  as  will  be  seen,  the  evidence  is  that 
plague  is  only  under  very  exceptional  circumstances  carried 
by  fomites. 

Typhus  not  carried  in  Clothing.  —  When  typhus  fever 
appeared  in  New  York  in  1892,  from  sixty  to  seventy-five 
officers  of  the  health  department  were,  according  to  Doty,^ 

'  Cited  by  Germano,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz., 
1897,  XXIV,  404. 

2  Leviticus,  Chapter  xiii,  verses  47-59. 

3  Doty,  Med.  News,  N.  Y.,  1905,  LXXXVI,  730. 


INFECTION  BY  FOMITES  175 

more  or  less  in  contact  with  the  cases,  often  in  intimate  con- 
tact; gowns  were  not  used,  and  the  officials  went  freely  be- 
tween the  patients  and  their  own  homes,  and  about  their 
other  business,  yet  no  case  of  this  disease  could  be  traced  to 
fomites  infection. 

Butler  ^  speaks  of  a  parlor  maid  in  a  contagious-disease 
hospital  who  for  six  months  had  been  in  daily  contact  with 
nurses  coming  directly  from  scarlet-fever  cases  without  change 
of  clothes,  but  she  did  not  contract  the  disease  until  exposed 
to  an  incipient  case  in  the  person  of  a  nurse,  when  she 
promptly  developed  scarlet  fever.  This  is  only  one  illustra- 
tion of  many  of  the  failure  of  supposedly  infected  clothing 
to  infect. 

Physicians  rarely  carry  Disease.  —  In  scarlet  fever  and 
diphtheria  physicians  are  constantly  passing  from  the  sick  to 
the  well.  Some  of  them  take  great  precautions  to  avoid 
carrying  the  disease  in  their  clothes,  but  the  majority  take 
few  or  none,  —  or  at  least  did  not  until  very  recently.  Yet 
records  of  their  transmitting  disease  are  extremely  rare.  For 
many  years  I  was  on  the  lookout  for  this  mode  of  transference, 
and  only  once  or  twice  found  any  evidence  that  the  phj^si- 
cian  was  at  fault.  Even  if  the  infection,  say  of  diphtheria, 
can  be  traced  to  the  physician,  which  is  most  likely,  that  the 
bacilli  were  carried  from  the  sick  to  the  well  in  his  clothes,  or 
even  that  they  were  on  his  unwashed  hands,  or  that  he  had 
become  a  carrier  and  they  were  growing  in  his  throat?  The 
relative  probability  of  the  first  hypothesis  is  so  small  that  it 
may  be  dismissed. 

Infection  by  Clothing  is  Rare.  —  If  the  gross  infection  of 
clothing  is  only  in  rare  instances  the  cause  of  disease,  how 
little  must  be  attributed  to  slight  infection!  A  few  droplets 
of  tuberculous  saliva,  a  slight  smear  of  moisture  from  the 
lips  of  a  diphtheria  patient,  will  soon  lose  their  virulence  after 
exposure  to  light  and  air.  But  usually  the  visitor  in  a  sick- 
room will  escape  all  infection  except  the  hypothetical  floating 
1  Butler,  Proc.  Roy.  Soc.  Med.,  Lond.,  1908, 1,  Epidemiol.  Sec,  225. 


176         THE  SOURCES  AND  MODES  OF  INFECTION 

particles.  The  danger  from  this  floating  matter  will  be  shown 
in  another  chapter  to  be  a  negligible  quantity.  It  is  the  com- 
mon practice  for  physicians,  nurses  and  visitors  in  a  room 
occupied  by  a  contagious  case  to  wear  a  gown  and  cap.  For 
physicians  and  nurses  who  are  to  move  or  lift  the  patient,  or 
otherwise  come  into  intimate  contact  with  him,  the  gown  is 
a  reasonable  protection  against  possible  gross  contamination. 
For  the  careless  visitor  too  it  may  be  useful.  The  cap  is  a 
useless  frivolity.  It  is  amusing  to  see  how  religiously  it  is 
worn,  while  no  protection  is  given  the  feet,  though  Denny 
and  Nyhen^  have  shown  that  infection  by  means  of  the  shoes 
is  bacteriologically  possible,  while  the  aerial  infection  of  the 
hair  has  never  been  demonstrated  and  is  highly  improbable. 
More  than  once  have  I  seen  a  physician  don  his  cap  to  keep 
the  germs  from  flying  into  his  hair,  and  pass  freely  from  one 
diphtheria  patient  to  another,  inspecting  the  throat,  feeling 
the  pulse  or  smoothing  the  bedclothes,  and  occasionally 
stroking  his  own  chin  or  scratching  his  head,  all  without 
washing  his  hands.  And  physicians  and  nurses  will  continue 
to  do  such  things  as  long  as  they  fancy  that  air  infection  is 
all  they  have  to  fear,  and  forget  that  there  is  such  a  thing  as 
contact  infection.  It  has  for  some  years  been  my  custom 
not  to  wear  a  gown  when  called  in  consultation  to  cases  of 
contagious  disease,  or  when  visiting  hospital  wards,  unless  I 
am  to  do  much  work  about  the  patient.  Under  the  condi- 
tions of  a  casual  visit,  even  in  smallpox,  I  do  not  wear  a 
gown.  It  is  not  necessary  to  touch  anything  except  with  the 
hands,  and  these  should  be  carefully  washed  before  leaving. 
I  have  never  carried  infection  to  my  home,  or  elsewhere  so 
far  as  known,  and  I  believe  that  there  is  no  chance  of  my 
doing  so. 

Laundries  and  Disease.  —  If  clothing  can  carry  infection, 

sickness  ought  to  make  its  appearance  in  laundries,  to  which 

enormous  quantities  of  clothing  go  even  while  the  infecting 

material  is  still  fresh.     Attempts  have  been  made  to  show 

'  J.  Mass.  Ass.  Bds.  of  Health,  Bost.,  1904,  XIV,  109. 


INFECTION  BY  FOMITES  177 

that  disease  is  carried  to  laundry  workers  in  this  wa}^,  and 
it  is  probable  that  some  of  the  alleged  instances  are  true. 
Thus  SedgVk'ick,  and  also  Walcott/  report  cases  of  typhoid 
fever  where  the  evidence  was  very  strong  that  the  disease 
was  contracted  by  handling  soiled  linen.  Thorne-Thorne  ^ 
also  reports  an  interesting  case  of  probable  transmission  of 
typhoid  fever  bj^  clothing.  That  such  accidents  are  common 
has  never  been  shown.  Certainly  in  Providence  there  is  no 
excess  of  scarlet  fever,  diphtheria  or  typhoid  fever  among 
laundry  workers.  This  cannot  be  due  to  the  disinfection  of 
the  clothing,  for  much  disinfection  is  not  efTective,  and  for 
six  years  there  has  been  no  disinfection  after  diphtheria, 
and  moreover  the  linen  from  carriers  and  missed  cases  is 
nowhere  subjected  to  disinfection. 

It  is  true  that  Landouzy,^  after  examining  1590  laundry 
workers  in  Paris,  states  that  tuberculosis  is  twice  as  prevalent 
among  them  as  among  other  workers,  and  he  attributes  it  to 
infection  from  soiled  clothing.  But  certainly  other  occu- 
pations show  an  even  greater  excess  of  this  disease,  and 
there  is  no  suggestion  that  it  is  due  to  infection  from  the 
materials  handled.  There  may  be  many  other  reasons  why 
laundry  workers  should  show  an  excess  of  tuberculosis,  such 
as  age  distribution,  poverty  and  overwork. 

Infection  of  Rooms.  —  It  is  generally  believed  that  the 
room,  or  rooms,  which  have  been  occupied  by  a  case  of  con- 
tagious disease  are  a  fertile  source  of  danger  to  others.  The 
germs  of  diphtheria,  scarlet  fever  and  smallpox  are  sup- 
posed to  become  attached,  not  only  to  books,  playthings, 
l)edding  and  furniture,  but  also  to  the  walls  and  ceilings.  It 
is  true  that  anything  which  can  be  reached  by  the  patient 
or  attendant  may  possibly  receive  infection,  the  chance  in- 
creasing according  to  the  frequency  with  which  the  thing  is 

>  Sedgwick  and  Walcott,  J.  Mass.  Ass.  Bds.  Health,  Boston,  1900, 
IX,  145. 

2  Thorno-Thorno,  Clin.  Soo.  Trans.,  Lond.,  1S92,  XXV,  Suppl.,  67. 
'  Landouzy,  I'rcsse  mcd.,  Par.,  1905,  XIII,  033. 


178         THE  SOURCES  AND  MODES  OF  INFECTION 

handled.  That  parts  of  the  room  or  its  contents  not  touched 
should  be  infected  by  floating  particles,  is  highly  improbable. 
The  secretions  and  excretions  which  in  various  ways  become 
attached  to  the  contents  of  the  room  are  usually  small  in 
amount  and  thinly  smeared  on  the  surface.  Such  material 
usually  rapidly  loses  its  virulence  by  drying,  so  that,  as  is 
shown  in  these  pages,  virulent  germs  are  recovered  from  the 
sick-room  in  only  a  small  proportion  of  tests.  Nevertheless 
if  people  should,  after  the  termination  of  the  sickness,  crowd 
into  the  room,  rub  their  moistened  fingers  over  the  various 
objects  and  put  the  fingers  in  the  mouth,  infection  might 
sometimes  result.  But  as  the  germs  die  rapidly,  as  probably 
not  many  persons  enter  the  room,  as  even  visitors  would 
usually  run  little  chance  of  taking  up  whatever  pathogenic 
organisms  might  be  there,  we  are,  I  think,  justified  in  assum- 
ing that  infection  from  the  room  or  its  contents  is  not  very 
likely  to  take  place. 

"  Lung  Blocks."  —  The  celebrated  "  lung  block  "  in  New 
York,  bounded  by  Cherry,  Catherine,  Market  and  Hamilton 
streets,  has  had  enormous  influence  on  modern  views  con- 
cerning the  transmission  of  tuberculosis.  The  great  excess 
of  tuberculosis  in  certain  tenement  houses  has  given  rise  to 
a  strong  belief  in  its  causation  by  infection  which  remains 
attached  to  the  interior  of  the  dwelling.  We  even  hear  much 
loose  talk  about  the  germs  of  the  disease  developing  in  the 
filth  and  dampness  of  these  dark  houses.  What  an  important 
factor  house  infection  is  believed  to  be  in  the  causation  of 
this  disease  is  well  illustrated  by  the  exceedingly  prominent 
place  which  is  given  to  room  disinfection.  To  judge  from  the 
attention,  time  and  money  bestowed  on  room  disinfection 
after  the  removal  or  death  of  a  consumptive,  this  practice 
is  considered  of  equal  importance  with  hospitals,  sanatoriums, 
dispensaries  or  district  nursing  as  a  preventive  measure.  Let 
us  see  what  is  the  evidence  on  which  house  infection  is  sup- 
posed to  rest.  It  is  apparently  that  cases  continue  to  occur 
in  the  same  house  during  successive  years.    This  judgment 


INFECTION  BY  FOMITES  179 

is  based  on  the  spot  map.  Thus  in  New  York^  during  five 
years,  42  per  cent  of  the  deaths  from  tuberculosis  occurred  in 
23  of  the  total  houses  infected,  or  in  5.25  per  cent  of  all  the 
houses  in  the  city.  In  Ward  IV,  55.8  per  cent  of  the  cases 
occurred  in  10.5  per  cent  of  the  houses  in  the  ward  and  in  28 
per  cent  of  the  infected  houses.  In  Ward  VI,  44.7  per  cent  of 
the  cases  were  in  7  per  cent  of  the  total  houses  and  in  19 
per  cent  of  the  infected  houses.  Many  in  other  cities  have 
noted  the  same  phenomenon,  but  it  has  been  especially  well 
recorded  by  the  New  York  Department  of  Health.  But  to 
say  that  these  facts  are  to  be  largely  explained  by  the  per- 
sistence of  the  tubercle  bacilli  in  the  houses  is  no  more  rea- 
sonable than  it  would  be  to  explain  the  recurrence  of  an  excess 
of  murders  in  certain  areas  to  the  persistence  of  a  hypothet- 
ical microbe  of  homicide.  It  is  true  that  the  advocates  of 
the  importance  of  house  infection  point  to  numerous  in- 
stances in  which  an  apparently  healthy  family  moving  into 
a  house  recently  occupied  by  a  consumptive  later  develop 
the  disease.  That  such  should  quite  often  happen  merely  as 
a  coincidence  is  necessitated  by  the  great  prevalence  of  the 
disease.  That  in  "  lung  blocks  "  exposure  to  living  cases  in 
the  other  tenements  is  a  much  more  likely  source  of  the 
disease  than  exposure  to  bacilli  on  the  walls,  is  probable.  To 
demonstrate  the  relation  of  the  disease  to  house  infection  it 
would  be  necessary  to  go  fully  into  the  history  of  at  least  a 
large  proportion  of  the  cases,  and  that,  particularly  as  we 
really  know  nothing  about  the  latent  period  of  the  disease, 
is  at  present  impossible.  The  excessive  incidence  of  tubercu- 
losis on  certain  houses  is  no  proof  of  house  infection,  and  we 
are  obliged  to  appeal  to  the  facts  of  bacteriology  and  the 
general  principles  of  infection  to  estimate  the  probable  dan- 
ger from  this  source.  When  we  consider  the  number  of  per- 
sons who  are  continually  throwing  off  great  numbers  of 
tubercle  bacilli,  and  the  numberless  chances  there  are,  particu- 
larly in  the  crowded  tenement  districts,  of  coming  in  contact 
'  Rep.  Dept.  Health,  City  of  New  York,  1896,  244. 


180         THE  SOURCES  AND  MODES  OF  INFECTION 

with  fresh  infective  material,  there  seems  to  be  no  necessity 
of  assuming  that  infection  must  be  traced  to  the  more  or  less 
feeble  and  scattered  germs  that  may  be  clinging  to  the  walls 
of  a  vacated  apartment.  What  necessity  or  excuse  is  there 
for  assuming  that  such  infection  plays  more  than  an  inap- 
preciably minute  part  in  the  causation  of  this  disease  ? 

Rags  and  Disease.  —  Rags  have  often  been  considered  an 
important  vehicle  of  disease.  At  one  time  much  attention 
was  given  to  this  subject  in  the  United  States,  and  great 
danger  was  apprehended  from  the  importation  of  foreign  rags, 
and  stringent  measures  were  taken  to  secure  their  disinfec- 
tion. Lengthy  discussions  of  the  matter,  and  references  to  a 
great  volume  of  literature,  may  be  found  in  a  report  for  the 
New  York  City  Board  of  Health  by  Smith  in  1886,  and  in  the 
Marine  Hospital  Report  for  1893.^  Numerous  references 
are  given  of  the  alleged  transmission  of  various  diseases  by 
means  of  rags.  Among  the  diseases  mentioned  are  smallpox 
(126  outbreaks),  influenza,  scarlet  fever,  erysipelas,  typhoid 
fever,  septicemia,  cholera,  and  a  disease  peculiar  to  rag  dust, 
called  "  flock  cough." 

Rags  and  Smallpox.  —  It  has  been  believed  that  small- 
pox is  frequently  introduced  among  the  workers  in  paper 
mills  by  the  rags  which  they  handle.  Numerous  instances 
have  been  reported  from  Maine,  Massachusetts  and  Wiscon- 
sin, as  well  as  from  foreign  countries.  Most  of  the  evidence 
is  very  inconclusive,  as  no  effort  is  made  to  exclude  other 
sources  of  infection,  and  the  disease  is  usually  prevailing 
generally  at  the  time.  The  most  suggestive  outbreaks  are  a 
series  reported  by  the  Massachusetts  State  Board  of  Health.^ 
Here  from  one  to  three  cases  occurred  in  six  mills  in  different 
localities  at  a  time  when  there  was  no  smallpox  in  the  town. 
Dr.  Abbott,  who  personally  studied  these  outbreaks,  was  con- 
vinced that  they  were  due  to  handling  rags.  Yet  it  is  curious 
that  almost  nothing  has  been  heard  of  this  sort  of  infection 

'  Rep.  Surg.  Gen.  U.  S.  Mar.  Hosp.  Serv.,  1893,  II,  330. 
*  Rep.  St.  Bd.  Mass.,  1888,  xvi. 


INFECTION  BY  FOMITES  181 

during  the  last  twenty  years,  and  this  at  a  time  when  small- 
pox was  of  a  remarkably  mild  type  and  great  quantities  of 
clothing  worn  by  patients  must  have  escaped  disinfection. 
Abbott  was  also  convinced  that,  owing  to  the  length  of  time 
between  the  collection  of  the  rags  and  the  opening  of  the 
bales,  no  danger  was  to  be  apprehended  from  foreign  rags. 
Doty^  says  "  that  the  most  careful  investigation  has  failed 
to  present  satisfactory  evidence  that  either  foreign  or  domes- 
tic rags  act  as  a  medium  of  infection."  He  has  personally 
carefully  studied  the  question  in  Egypt,  where  many  rags  are 
collected  for  the  American  market,  and  he  says  that  there  is 
no  evidence  of  the  infection  of  the  handlers  of  even  the  fresh 
rags. 

Rugs  and  Plague.  —  Remlinger^  has  recently  called  atten- 
tion to  the  supposed  danger  to  be  apprehended  from  draper- 
ies, and  particularly  also  rugs,  from  the  Orient.  He  rightly 
says  that  many  of  the  rugs  are  very  filthy,  and  must  have 
been  infected  during  their  use  or  manufacture.  Yet  during 
all  the  prevalence  of  cholera  and  bubonic  plague  in  Asia  dur- 
ing recent  years  not  a  single  case  of  these  diseases  has  been 
brought  into  Europe  or  America  in  this  way,  though  great 
quantities  of  rugs,  draperies  and  rags  have  been  imported 
without  disinfection  or  with  very  imperfect  disinfection. 

Money  and  Disease.  —  Money  is  popularly  believed  to  be 
a  common  means  of  spreading  disease.  Indeed  there  are  few 
things  which  at  first  sight  seem  more  likely  to  do  so  than  paper 
money.  Germs  readily  become  attached  to  its  surface,  it 
passes  rapidly  from  one  person  to  another,  it  is  kept  in  inti- 
mate contact  with  the  person,  held  closely  in  the  hand  and 
often  put  to  the  lips.  Nevertheless  there  is  no  good  evidence 
that  money  has  ever  actually  been  the  means  of  spreading 
contagious  disease.  If  money  is  frequently  a  carrier  of  infec- 
tion, persons  who  handle  a  great  deal  of  money  ought  to  be 
particularly  subject  to  infectious  disease.    Tliis  does  not  seem 

•  Doty,  Med.  Roc,  N.  Y.,  1900,  LVIII,  681. 

*  Remlinger,  Hyg.  g6n.  ct  appliq.,  P;ir.,  1907,  II,  257. 


182        THE  SOURCES  AND  MODES  OF  INFECTION 

to  be  the  case,  though  there  are  unfortunately  no  good  pub- 
hshed  statistics  bearing  on  the  subject.  However,  it  is  the 
business  of  the  supporters  rather  than  the  opponents  of  the 
theory  to  produce  the  figures.  I  have  been  on  the  lookout 
for  contagious  disease  among  bank  clerks,  but  the  very  few- 
cases  that  have  come  to  my  knowledge  during  the  past 
twenty-five  years  have  evidently  been  contracted  in  other 
ways.  According  to  Hilditch,^  the  "United  States  treasurer, 
who  has  given  the  subject  long  and  careful  consideration,  is 
emphatic  in  his  statement  that  '  there  is  not  the  slightest  evi- 
dence to  show  that  the  employees  in  his  department  contract 
infectious  diseases  any  oftener  than  others  who  are  not  in 
this  line  of  work.'  "  It  may  be  argued,  and  there  is  some 
truth  m  this,  that  tellers  are  accustomed  to  take  considerable 
precaution,  such  as  keeping  the  fingers  away'  from  the  lips 
and  washing  the  hands  before  eating.  Tram-car  conductors 
are,  however,  I  know  from  observation,  particularly  prone  to 
hold  bills  and  coins  between  the  lips,  and  are  in  other  ways 
extremely  careless,  yet  they  certainly  show  no  excess  of  scarlet 
fever,  diphtheria  or  smallpox.  A  bacteriological  study  of 
paper  money  has  been  made  by  Hilditch  above  referred  to. 
He  examined  twenty-four  bills  and  found  the  number  of  bac- 
teria varied  from  14,000  to  586,000  per  bill.  Pus  bacteria 
were  found,  as  was  to  have  been  expected,  but  no  other  patho- 
genic forms.  Hilditch  could  find  accounts  of  only  four  other 
similar  investigations,  none  of  which,  however,  were  as 
thorough  as  his.  Bacteria  are  not  found  in  any  large  num- 
bers on  coins,  chiefly  because  of  the  germicidal  action  of  the 
metal,  as  shown  by  the  researches  of  Park,^  Vincent  ^  and 
Bolton. 

Much  Evidence  Unsatisfactory.  —  It  would  be  easy  to  find 
hundreds  of  alleged  instances  of  fomites  infection,  in  some 
of  which  the  infection  was  supposed  to  have  persisted  for 

1  Hilditch,  Pop.  Sc.  Month,  N.  Y.,  1908,  LXXIII,  157. 

2  Cited  by  Hilditch. 

'  Vincent,  Abst.  Med.  News,  N.  Y.,  1892,  LXXX,  275 


INFECTION  BY  FOMITES  183 

years.  Those  mentioned  in  the  preceding  pages  are  only  a 
few  which  I  happened  to  have  at  hand.  In  most  of  them 
there  is  no  real  evidence  that  the  disease  was  produced  in  the 
manner  claimed.  The  error  made  in  claiming  so  much  for 
fomites  infection  in  yellow  fever  shows  how  great  is  the  lia- 
bility of  error  for  other  diseases. 

Persons,  not  Things,  are  Dangerous.  —  It  must  also  be 
borne  in  mind  that  in  very  man}'  of  the  reported  cases  the 
supposed  infected  articles  were  carried  by  some  person.  That 
the  person  may  be  the  "carrier"  of  living  germs  on  his  own 
mucous  surfaces,  though  showing  no  symptoms,  we  now  know 
full  well.  Until  recently  this  was  not  known,  hence  it  was 
universal  to  consider  things,  not  persons,  as  the  bearers  of 
infection.  We  can  now  see  that  persons  in  whom  the  germs 
are  growing  are  much  more  likely  to  be  the  agents  of  infec- 
tion than  are  things  on  which  the  germs  are  dying.  Some  of 
the  instances  of  alleged  fomites  infection,  such  as  the  room 
infection  in  scarlet  fever  referred  to,  are  doubtless  really 
instances  of  carrier  infection. 

Fomites  and  Tetanus.  —  It  is  not  for  a  moment  to  be 
assumed  that  there  are  no  instances  of  fomites  infection.  It 
is  not  impossible,  or  at  all  improbable,  that  occasionally 
typhoid  fever,  smallpox,  diphtheria  and  other  diseases  are 
caused  by  material  things  holding  the  living  bacteria  for  some 
weeks  or  even  for  months.  In  some  instances  the  clinical 
evidence  of  fomites  infection  is  very  strong,  though  perhaps 
it  can  rarely  if  ever  be  in  any  individual  instance  entirely 
conclusive.  If  it  can  be  substantiated  by  bacteriological  evi- 
dence, it  becomes  so  much  the  stronger.  The  strongest  evi- 
dence we  have  of  fomites  infection  is  concerning  anthrax  and 
tetanus.  This  is  not  surprising  when  it  is  recalled  that  the 
bacilli  of  both  of  these  diseases  are  spore-forming  and  capable 
in  that  state  of  resisting  unfavorable  conditions  of  life  for 
years.  Thus  Smith'  finds  that  tetanus  bacilli  will  survive 
boiling  for  sixty  minutes  at  a  time,  or  twenty  minutes  on 
'  Smith,  Theobold,  J.  Am.  M.  Ass.,  Chicago,  1908,  L,  929. 


184         THE  SOURCES  AXD  MODES  OF  INFECTION 

each  of  three  successive  days.  This  explains  why  they  have 
been  found  ahve  and  virulent  in  commercial  gelatine  and  in 
that  situation  have  been  known  to  give  rise  to  the  disease  in 
human  beings.^  Of  six  samples  of  cotton  lamp  wick  pur- 
chased in  various  shops  in  Havana,  five  were  shown  by  the 
inoculation  of  white  mice  to  be  infected  with  tetanus.  This 
material  was  used  by  midwives  for  tying  the  umbilical  cord, 
and  after  sterile  material  was  furnished  them  by  the  depart- 
ment of  health  it  is  said  that  almost  no  deaths  from  infantile 
tetanus  occurred  in  Havana.^  The  number  of  deaths  from 
tetanus  in  children  under  one  year  of  age  in  Havana  decreased 
from  128  in  1901  to  18  in  1908.  Some  of  the  Fourth  of  July 
tetanus  is  believed  to  be  due  to  the  presence  of  the  spores 
in  the  wads  of  blank  cartridges,  and  they  were  demonstrated 
in  them  by  Dolley,^  and  are  said  to  have  been  found  in  car- 
tridges in  Germany  byMusehold  of  Strassburgand  others,  but 
several  other  American  observers  failed  to  find  tetanus  germs 
in  a  total  of  759  cartridges  examined. 

Fomites  and  Anthrax.  —  The  spores  of  anthrax  are  so 
resistant  that  they  have  been  kept  for  ten  or  twelve  years, 
but  the  bacilli  themselves  do  not  survive  any  longer  than 
typhoid  bacilli.  Anthrax,  though  rather  rare  in  the  United 
States  and  England,  is  very  common  in  some  parts  of  the 
world,  particularly  in  Asia,  and  the  spores  are  frequently 
imported  in  dry  animal  products  from  Asiatic  countries. 
Legge*  cites  from  several  observers  who  recovered  the  spores 
from  hair  and  hides  imported  from  China  and  Siberia.  More 
recently  Eurich'^  has  examined  nearly  750  specimens  of  wool, 
hair  and  dust  from  these  materials.     In  over  600  specimens 

'  Tuck,  Jour.  Path.  &  Bacteriol.,  Edinb.  &  Lond.,  1904,  IX,  38. 

^  Junta  Sup.  de  San.  de  la  Isla  de  Cuba,  Supplemento  y  Note  Adi- 
cional,  1902-03,  4. 

^  Dolley,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  466. 

*  Legge,  Lancet,  Lond.,  1905, 1,  694,  and  Rep.  Insp.  of  Fact.,  Lancet, 
Lend.,  1904,  I,  1206. 

6  Rep.  Anthrax  Investigation  Bd.,  Bradford,  Eng.,  No.  3,  1908,  8. 


INFECTION  BY  FOMITES  185 

free  from  blood  he  found  no  anthrax  germs,  but  he  did  find 
them  in  20,  or  14.4,  per  cent,  of  139  bloodstained  specimens. 
These  findings  are  substantiated  in  his  last  report  (1909),  and 
he  speaks  of  a  case  of  anthrax  in  a  man  who  handled  wool 
in  which  anthrax  spores  were  actually  found.  In  G4  samples 
of  dust,  anthrax  germs  were  demonstrated  only  oncc.^  Page^ 
also  gives  references  to  other  similar  findings.  But  such 
observations  are  not  necessary  to  show  that  the  disease  is 
transported  in  this  way,  for  there  is  ample  clinical  evidence 
that  such  goods  are  the  direct  cause  of  anthrax  in  men  and 
animals.  In  fact,  most  industrial  anthrax  in  Western  Europe 
and  North  America  is  caused  by  handling  wool,  hair  and 
hides  imported  from  anthrax-infested  countries. 

Fomites  and  Typhoid  Fever.  —  One  of  the  most  remarkable 
of  the  authenticated  instances  of  fomites  infection  is  the 
transmission  of  typhoid  fever  by  means  of  army  blankets 
from  South  Africa.'  These  blankets  came  from  Africa  in 
October,  1902,  and  were  then  sold.  They  went  to  290 
different  parties.  One  lot  used  on  the  transport  Cornwall 
apparently  gave  rise  to  the  disease  in  May,  1903;  the  use 
of  another  lot  in  England  was  also  followed  by  typhoid 
fever.  Some  of  the  blankets  were  considerably  soiled,  and 
living  bacilli  were  found  on  several  that  were  examined  in 
London. 

Fomites  and  Diphtheria.  —  A  young  man  working  in  a 
laboratory  in  an  American  city. spilled  some  bouillon  culture 
of  diphtheria  bacilli  on  his  coat.  This  coat,  without  disin- 
fection, he  wore  when  calling  on  the  young  woman  to  whom 
he  was  engaged,  and  she  developed  diphtheria  two  days  later. 
The  culture  which  was  spilled  contained  only  the  branching 
forms  of  the  diphtheria  bacillus,  and  the  culture  from  the 
patient's  throat  showed  the  same  forms. 

But  very  few  instances  other  than  the  above  are  on  record 

'  Rep.  of  Chief  Inspector  of  Factories  and  Workshops,  1907,  57. 
2  Page,  J.  Hyg.,  Cambridge,  l{K)n,  LX,  3.57. 
'  Parkes,  Practitioner,  Lond.,  1903,  LXXI,  297. 


vl86         THE  SOURCES  AND  MODES  OF  INFECTION 

where  pathogenic  bacteria  have  actually  been  found  on  mate- 
rials which  presumably  have  carried  infection.  According  to 
Simpson/  plague  bacilli  were  found  by  Kitasato  on  cotton 
goods  imported  into  Japan,  and  this  was  thought  by  Kitasato 
to  be  the  way  in  which  the  disease  was  introduced  into  that 
country,  but  from  what  is  now  known  about  the  mode  of 
extension  of  the  disease  this  seems  highly  improbable. 

Few  Instances  of  Fomites  Infection.  —  But  while  we  may 
admit  that  occasionally  the  virus  of  even  many  of  the  com- 
moner diseases  may  be  retained  on  fomites  for  a  considerable 
length  of  time,  and  ultimately  give  rise  to  new  cases,  there 
is  no  clinical  evidence  to  show  that  such  instances  are  at  all 
common.  Even  when  carefully  sought  for,  fomites  infection 
is  not  very  often  found.  In  my  early  work  as  health  officer 
I  firmly  believed  in  the  importance  of  this  factor,  and  dili- 
gently sought  for  evidence.  The  fact  that  I  found  very  little 
was  one  thing  which  led  to  a  more  careful  consideration  of  the 
subject.  Of  13,970  cases  of  scarlet  fever  reported  in  Michi- 
gan,^ only  335  were  attributed  to  fomites  infection.  To  an 
even  less  degree  are  diphtheria  and  measles  attributed  in 
this  report  to  fomites  infection.  Of  221  cases  of  bubonic 
plague  in  Natal, ^  only  8  were  by  Hill  attributed  to  fomites 
infection,  and  Mitchell  in  Port  Elizabeth  attributed  only 
6  of  337  cases  to  the  same  source.  When  we  consider  that 
most  of  the  evidence  is  extremely  flimsy,  and  that  much  of 
the  alleged  fomites  infection  is  probably  carrier  infection,  and 
remembering  also  how  the  history  of  yellow  fever  has  taught 
us  to  be  wary  of  such  proofs,  we  are  forced  to  the  conclu- 
sion that  there  is  little  in  the  history  of  the  more  prevalent 
infectious  diseases  to  indicate  that  fomites  infection  is  at  all 
common. 

Reasons  for  Belief  in  Fomites.  —  One  reason  why  fomites 
infection  looms  so  large  in  the  minds  of  health  officers,  as 

*  Simpson,  Treatise  on  Plague,  Cambridge,  1905,  204. 

2  Rep.  St.  Bd.  Health,  Mich.,  1906,  134. 

3  J.  Hyg.,  Cambridge,  1907,  VII,  712. 


INFECTION  BY  FOMITES  187 

well  as  of  the  laity,  is  that  the  striking  character  and  air 
of  mystery  about  the  alleged  incidents  are  so  impressive. 
"  Death  in  a  Toy,"  or  "  A  Child  Succumbs  to  the  Dread 
Disease  from  Infection  Lurking  in  its  Mother's  Shawl," 
appeal  to  the  imagination.  That  the  invisible  emanations  of 
disease  should  cling  to  a  garment  for  years  is  too  near  akin 
to  the  stories  of  the  Arabian  Nights  not  to  impress  the  average 
mind.  Hence  it  is  that  the  comparatively  few  instances  of 
real  fomites  infection  have  far  more  than  their  due  weight 
in  our  estimation  of  the  relative  importance  of  different  modes 
of  infection. 

Even  if  all  the  alleged  instances  of  fomites  infection  were 
true,  the  amount  of  disease  apparently  caused  in  this  way 
is  relatively  very  small.  The  frequency  with  which  conta- 
gious disease  can  be  traced  to  fomites  is  not  the  reason  for 
the  general  belief  in  the  importance  of  this  mode  of  infection. 
The  real  reason,  I  have  no  doubt,  is,  that  until  very  recently 
there  seemed  to  be  no  other  way  of  explaining  isolated  cases 
of  di-sease.  As  a  rule  it  is  impossible,  even  with  modern  aids 
to  the  diagnosis  of  obscure  cases,  to  trace  the  source  of  infec- 
tion of  most  cases  of  contagious  disease,  particularly  in  cities. 
The  theory  of  long  persistent  fomites  infection  seemed  to 
offer  a  reasonable  solution,  and  hence  met  with  universal 
acceptance.  The  theory  was  almost  a  necessitj^  to  explain 
the  facts  as  they  were  formerly  understood.  Now  we  have 
no  need  for  such  a  theory,  and  a  much  more  satisfactory 
explanation  is  at  hand. 

Evidence  against  Theory.  —  It  is  only  within  a  very  few 
years  that  the  frequency  with  which  mild  atypical  cases  of 
disease  occur  has  been  recognized,  and  the  existence  of 
numerous  entirely  healthy  carriers  is  a  modern  discovery, 
which  is  even  now  denied  by  some.  The  more  carefully 
individual  cases  and  outbreaks  of  disease  are  studied,  the 
more  often  are  they  traced  to  missed  cases  and  carriers. 
It  is  not  probable  that  we  shall  ever  be  able  to  discover  the 
origin  of  all  our  contagious  disease.    We  can  only  infer  its 


188         THE  SOURCES  AND  MODES  OF  INFECTION 

source  from  the  data  we  have.  As  was  shown  in  the  first 
chapter,  there  is  every  reason  for  thinking  that  disease  germs 
rarely  grow  outside  of  a  hving  body.  Two  other  theories 
are  open  to  us.  Disease  may  be  due  to  the  persistence  of 
infection  on  things,  or  it  may  be  due  to  exposure  to  mild 
cases  or  carriers.  There  should  be  no  hesitancy  in  choosing 
between  the  danger  from  rapidly  dying  germs  on  books, 
money,  furniture  or  clothes,  and  rapidly  growing  germs  in  the 
mouth,  nose  and  intestines  of  persons.  Moreover  things 
must  be  carried,  people  move  freely  at  will. 

If  the  danger  from  fomites  infection  were  as  great  as  is 
generally  believed,  the  contagious  diseases  would  be  much 
more  common  than  they  are.  The  advocates  of  this  theory 
are  constantly  telling  us  how  easily  everything  near  the  sick 
becomes  infected  and  how  long  the  infection  lasts.  Every 
one  knows  that  at  the  best  disinfection  is  imperfect,  and  that 
much  that  passes  for  disinfection  is  no  disinfection  at  all. 
Then  the  missed  cases,  which  all  admit  occur  in  considerable 
numbers,  to  say  nothing  of  the  carriers,  are  constantly  infect- 
ing large  numbers  of  things  which  are  not  subjected  to  any 
disinfection.  Yet  our  scarlet  fever  and  diphtheria  are  not 
increasing,  which  means  that  one  case  of  the  disease  gives  rise 
to  no  more  than  another  case.  If  fomites  infection  occurred 
as  easily  as  is  alleged,  each  case  would  ramify  through 
fomites  into  a  dozen  more  cases.  One  reason  for  doubt  about 
the  prevailing  ideas  of  fomites  infection  is  this:  if  fomites 
infection  were  as  common  and  as  easy  as  is  alleged,  few 
could  escape  it,  and  the  infectious  diseases  would  be  much 
more  prevalent  than  they  are.  As  was  shown  in  Chapter  IV, 
the  chances  for  the  transfer  of  fresh  infective  material  are  so 
extremely  numerous  that  there  is  no  necessity  for  assuming 
the  far  more  difficult  and  uncertain  modes  of  aerial  convection 
and  transmission  by  fomites,  and  indeed  there  seems  to  be 
Httle  opportunity  for  their  action. 

Bacteriological  Evidence.  —  Having  considered  some  of 
the  clinical  evidence  of  the  part  played  by  fomites  in  the 


IXFECTIOX  BY  FOMITES  189 

transmission  of  infection,  it  is  desirable  to  inquire  what  light 
the  laboratory  study  of  disease  has  thrown  on  the  problem. 
One  of  the  first  labors  of  the  discoverer  of  a  pathogenic  organ- 
ism is  to  determine  its  resistance  to  various  hostile  influences, 
such  as  heat,  cold,  drying,  light  and  disinfectants. 

The  Effect  of  Drying  upon  Bacteria.  —  Drying,  exposure 
to  light  and  lack  of  nourishment  are  the  principal  factors 
which  determine  the  life  of  micro-organisms  on  fomites. 
Besides  the  study  of  the  germs  of  special  disease  by  those 
particularly  interested,  Germano,  whose  work  is  mentioned 
in  the  chapter  on  aerial  infection,  Ficker,^  Zonchello,'  Heim,^ 
and  Buckley,'*  among  others,  have  given  careful  and  system- 
atic attention  to  the  effect  of  drying  on  the  vitality  of  bac- 
teria. Exceedingl}^  divergent  results  have  been  reported  by 
these  different  observers.  This,  however,  is  not  surprising  if 
the  number  of  factors  involved  is  taken  into  consideration. 
Among  the  most  important  of  these  factors  is  the  amount 
of  light.  Germs  that  are  killed  in  a  few  minutes  in  direct 
sunlight  may  live  for  weeks  in  a  dark  place  or  even  in  diffused 
light.  The  thicker  the  layer  of  infectious  material,  the  longer 
is  its  virulence  likely  to  be  maintained.  This  thickness 
depends  largely  upon  the  nature  of  the  medium.  In  a  dried 
watery  medium,  bacteria  may  die  quickly,  while  they  may 
survive  long  in  sputum  or  feces.  The  more  complete  the 
drying,  the  shorter  the  life,  and  alternate  drying  and  damp- 
ening is  unfavorable.  The  higher  the  temperature,  the 
sooner  the  germs  perish.  Their  vitality  also  varies  with 
the  rapidity  of  the  drying  process  and  the  material  on 
which  they  happen  to  be.  Old  cultures  die  sooner  than 
fresh  ones,  and  different  strains  have  different  powers  of 
resistance.     The  chemical  composition  of  the  medium  antl 

>  Ficker,  Ztschr.  f.  IIvk.  u.  Infectionskrankh.,  Leipz.,  190.S,  LIX,  367. 
»  Zonchello,  (Jiornalc  della  Roal  Soc.  Ifal.  d'  Isicno,  1905,  XXVII, 
489,  537. 

»  Hcirn,  Ztschr.  f.  IlyK.  u.  Infectionskrankh.,  I^ipz.,  1905,  L,  122. 
*  Buckley,  Pul).  Health,  Lond.,  1900-07,  XIX,  290. 


190         THE  SOURCES  AXD  MODES  OF  INFECTION 

the  presence  or  absence  of  other  organisms  may  have  an 
influence. 

The  spores  of  bacteria  are  so  resistant  that  we  should  natu- 
rally expect  the  diseases  caused  by  the  spore-forming  kinds 
to  be  readily  carried  on  fomites.  As  has  been  shown,  this  is 
true  of  anthrax  and  tetanus,  diseases  which  belong  to  this 
class. 

Typhoid  Bacilli.  —  Among  the  more  hardy  non-spore- 
forming  bacteria  is  the  bacillus  of  typhoid  fever.  In  the  first 
chapter  it  was  shown  that  in  the  presence  of  moisture,  as  in 
privy  vaults,  the  soil,  milk,  water,  etc.,  this  bacillus  some- 
times lives  for  some  months,  though  it  often  dies  out  in  a 
much  shorter  time.  It  remains  to  consider  the  duration  of 
its  life  when  in  a  more  or  less  dry  condition. 

Firth  and  Horrocks^  found  that  typhoid  bacilli  would  live 
on  khaki  for  78  days,  in  feces  dried  on  serge  for  9  to  17  days, 
on  serge  for  10  days  after  it  had  been  exposed  to  direct  sun- 
light for  50  hours.  PfuhP  says  that  dried  on  linen  they  lived 
97  days.  Germano^  cites  Gaffky  as  reporting  that  the 
typhoid  bacillus  would  live  for  3  months  when  in  a  dry  con- 
dition, and  that  Uffelmann  recovered  it  from  various  dry 
materials  after  a  period  of  from  21  to  80  days.  But  Germano 
suspects  that  the  substances  were  not  perfectly  dry.  Ger- 
mano himself  was  able  to  preserve  typhoid  bacilli  dried  on 
wood  or  linen  for  90  days,  but  when  he  inoculated  sterile 
dust  with  a  bouillon  culture,  the  bacilli  did  not  survive  over 
4  days  and  sometimes  perished  in  1  day.  Most  of  them 
died  off  very  rapidly.  Buckley  *  found  they  would  live  for 
from  5  days  when  dried  on  paper  in  a  room  to  119  days 
when  kept  on  wood  in  a  moist  chamber.  The  consensus  of 
opinion  seems  to  be  that  while  under  unfavorable  conditions, 

1  Firth  and  Horrocks,  Brit.  M.  J.,  Lond.,  1902,  II,  936,  1094. 
'  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  555. 
'  Germano,    Ztschr.    f.    Hyg.    u.    Infectionskrankh.,    Leipz.,    1897, 
XXIV,  403. 

'  Buckley,  Pub.  Health,  Lend.,  1906-07,  XIX,  290. 


INFECTIOX  BY  FOMITES  191 

as  when  quite  dry  and  exposed  to  light,  the  typhoid  bacillus 
may  die  in  a  few  days,  yet  under  conditions  which  must  fre- 
quently prevail  it  may  remain  alive  on  such  things  as  cloth- 
ing and  bedding  for  some  months, 

Mediterranean  Fever.  —  The  micrococcus  of  Mediterra- 
nean fever  has  about  the  same  resistance  as  that  of  typhoid 
fever.  Like  the  typhoid  bacillus,  it  is  killed  in  an  hour  or 
two  in  direct  sunlight.  Dried  on  glass  it  survives  16  days,  in 
moist  soil  72  days  and  on  a  blanket  80  days.^ 

Diphtheria.  —  Loeffler  kept  dry  diphtheria  bacilli  alive  for 
from  9  to  IG  weeks,  Roux  and  Yersin  for  5  months,  D'Espine 
and  Morignac  for  between  3  and  4  months,  and  Park  for  4 
months.^  Germane^  found  that  they  would  retain  their 
virulence  after  remaining  in  dry  earth  or  dust  for  20  to  40 
days,  and  Reyes*  found  them  virulent  in  sand  and  on  cloth 
after  14  days.  Buckley^  recovered  living  bacilli,  when  dried 
in  the  air  on  paper,  after  6  da3's,  on  wood  after  8  days,  on 
cotton  and  on  glass  after  24  days,  and  on  plastei"  after  37 
days.  Hill ''  exposed  to  ordinary  room  conditions,  glass  rods 
which  had  been  rubbed  on  a  culture  of  diphtheria  bacilli. 
Of  these  28  per  cent  survived  14  days  and  9  per  cent  20 
days.  Houston '  found  that  they  died  very  quickly  in  earth. 
Leighton'*  recovered  them  from  warm  moist  modeling  clay 
up  to  18  days.  Williams  ^  could  not  recover  the  germs 
after  24  hours  from  pencils  moistened  by  the  lips  of  patients 
who  had  the  bacilli  in  the  throat. 

1  Horrocks,  Rep.  Commission  Roy.  Soc,  Pt.  I,  1901. 

^  Cited  by  Germano. 

'  Germano,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1897, 
XXV,  439. 

*  Reyes,  Jahrb.  u.  d.  Fortschr.  .  .  .  d.  path,  mik.,  Baumgarten, 
1895,  XI,  203. 

5  Buckley,  Pul).  Health,  Lond.,  1906-07,  290. 

"  Hill,  Am.  Pub.  Health  Ass.  Rep.,  1902,  XXVIII,  209. 

'  Hoaston,  Rep.  Med. Off.  Loc.Gov.  Bd.,Lond.,  1898-99, XXXIII, 413. 

'  I.;eighton,  Pediatrics,  1901,  XII,  360. 

'  Williams,  N.  Y.  Health  Dept.,  Sci.  Bull.  2,  1895,  16. 


192         THE  SOURCES  AND  MODES  OF  INFECTION 

Dysentery  Bacilli.  —  According  to  Pf uhl  ^  the  bacillus  of 
dysentery  may  remain  alive  for  17  days  when  dried  on  cloth, 
or  10  days  when  in  dry  sand.  In  direct  sunlight  it  dies  in  30 
minutes.^  Kruse^  claims  that  when  dry  it  will  retain  its  vital- 
ity for  months. 

Tubercle  Bacilli.  —  More  attention  has  been  paid  to  the 
vitality  of  the  tubercle  bacillus  than  to  that  of  other  bacteria. 
It  is  generally  believed  to  be  one  of  the  most  resistant,  but 
Hill  *  has  shown  that  under  the  same  natural  conditions  of 
dryness,  light,  etc.,  the  diphtheria  bacillus  will  outlive  it. 
Many  of  the  earlier  writers  claimed  a  very  considerable  lon- 
gevity for  the  tubercle  bacilli  in  dried  sputum.  Villemin, 
Schill,  Fischer,  Koch,  De  Thoma,  Sormani,  Maffuci  and 
Cadeac  and  Malet  claimed  a  life  of  from  1  to  9  months.^ 
Ransome  and  Delepine "  found  that  the  bacilli  if  exposed  to  air 
and  light  would  not  survive  45  days,  but  if  kept  in  dim  light 
they  did  survive.  Twichell  ^  placed  sputum  in  a  folded  hand- 
kerchief, in  a  folded  carpet,  and  spread  on  wood,  and  ex- 
posed it  to  the  air  at  ordinary  temperatures  and  in  diffused 
light.  The  bacilli  survived  for  39  to  70  days.  In  sunlight 
they  died  in  a  few  hours.  Migneco  ^  found  that  when  dried 
on  cloth  in  the  sun  they  lived  from  20  to  30  hours. 

Not  so  Resistant  as  Believed.  —  Many  recent  observers 
do  not  find  this  bacillus  so  resistant  as  has  been  supposed. 
That  it  perishes  in  direct  sunlight  in  less  than  an  hour  seems 
certain.  Weinzirl,^  using  improved  methods,  finds  that  it 
will  not  survive  10  minutes,  and  frequently  dies  in  2  minutes. 

'  Pfuhl,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1902,  XL,  555. 
2  Shiga,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  765,  783. 
'  Kruse,  Deutsche  med.  Wchnschr.,  1901,  XXVII,  370,  386. 

*  Hill,  Am.  Pub.  Health  Ass.  Rep.,  1902,  XXVII,  209. 

*  Kolle  and  Wasserman's  Handbuch  [etc.],  Jena,  1903,  II,  108. 
^  Ransome  and  Delepine,  Proceedings  Royal  Society,  No.  336. 
'  Twichell,  Med.  News,  N.  Y.,  1905,  LXXXVII,  642. 

^  Migneco,  Arch,  of  Hyg.,  Mimchen  u.  Leipz.,  1895,  XXV,  361. 
"  Weinzirl,  J.  Infect.  Dis.,  Chicago,  1907  [Suppl.  No.  3],  128. 


INFECTION  BY  FOMITES  193 

Cadeac  ^  spread  sputum  on  marble  and  could  find  no  living 
germs  after  the  fourteenth  day.  On  a  porous  plaster  plate 
they  died  within  2  days.  Hill  ^  dried  sputum  on  glass  rods 
in  the  air  under  ordinary  room  conditions,  and  found  no  liv- 
ing bacilli  at  the  time  of  his  first  test,  which  was  made  after 
16  days.  Rickards,  Slack  and  Arms^  have  made  very  careful 
tests  by  exposing  sputum  on  wood  and  cloth  in  the  rooms  of 
ordinary  tenements.  They  find  that  when  dry  and  kept  in 
diffused  light  the  bacilli  will  live  about  I  month,  in  dark  and 
dry  rooms  up  to  85  days;  another  strain  survived  only  45 
days  under  the  latter  conditions.  Rosenau^  sa3^s  that  further 
work  upon  the  viability  of  the  dried  tubercle  bacillus  may 
change  our  views  as  to  its  hardiness,  and  failure  to  recognize 
lesions  produced  by  the  dead  bacillus  is  responsible  for  some 
of  the  false  conclusions  reached  by  certain  experimenters. 

Plague  Bacilli.  —  Simpson  ^  states  that  the  German  Plague 
Commission  found  that  in  a  large  number  of  experiments  with 
sputum,  blood,  etc.,  dried  on  all  sorts  of  materials,  under 
natural  conditions,  the  bacilli  of  bubonic  plague  do  not  sur- 
vive over  8  days.  Of  many  specimens  of  the  organism  dried 
on  cover  glasses  and  sent  to  England,  none  survived  the 
journey.  Kitasato®  found  that  plague  pus  dried  on  cover 
glasses  lost  its  virulence,  when  exposed  to  the  sun,  in  from 
3  to  4  hours,  and  this  has  been  substantiated  by  others.  As 
was  referred  to  in  the  first  chapter,  the  work  of  the  last  Eng- 
lish Plague  Commission  shows  that  virulent  plague  bacilli 
cannot  be  found  in  the  dirt  floors  of  native  houses  after  48 
hours.     According  to  the  careful  experiments  of  Buckley,^ 

'  Cadeac,  Lyon  m6d.,  1905,  CV,  865,  Abst.  Brit.  iM.  J.,  Lond., 
1906,  I. 

2  Hill,  Am.  Pub.  Health  Ass.  Rep.,  1902,  XXVIH,  209. 

3  Rickards,  Slack  and  Arms,  Am.  J.  Pub.  Hyg.,  Bost.,  1909,  V,  586. 
*  Rosenau,  U.  S.  Pul).  Healtli  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 

No.  57,  1909. 

'  Simpson,  Treatise  on  Plague,  Cambridge,  1905,  96. 

«  Kitasato,  Lancet,  I^nd.,  1894,  II,  428. 

'  Buckley,  Pub.  Health,  Lond.,  1906-07,  XIX,  290. 


194         THE  SOURCES  AND  MODES  OF  INFECTION 

plague  bacilli  remain  alive  after  drying  in  the  air,  for  11  hours 
when  dried  on  cotton,  2  hours  on  wood,  5  hours  on  plaster, 
2  hours  on  glass,  and  3  hours  on  paper.  When  kept  in  a 
desiccator  they  survived  on  cotton  for  22  hours,  and  in  a 
moist  chamber  for  only  36  hours.  Gotschlich,^  by  folding 
material  containing  the  germs  in  cloth,  could  preserve  them 
alive  for  from  3  to  4  weeks.  Simpson^  reports  that  infected 
cloth  may  retain  its  virulence  for  80  days.  According  to 
Verjbitski,^  the  crushed  viscera  of  experimental  animals  and 
the  crushed  bodies  of  fleas  when  smeared  on  cloth  and  dried 
will  preserve  the  bacilli  alive  for  130  days  at  a  temperature 
of  4-5°  C,  and  for  35  days  at  room  temperature.  Bandi  and 
Stagnitta-Balistreri  state  that  these  bacilli  may  survive  in  the 
bodies  of  dead  rats  for  2  months.  The  vitality  of  the  plague 
bacillus  has  been  carefully  investigated  by  Rosenau,*  who 
does  not  consider  it  a  frail  organism.  Temperature  is  the 
most  important  factor  in  its  life.  It  may  lose  its  virulence 
before  it  loses  its  vegetability.  It  dies  in  a  few  days  on  the 
dry  surface  of  hard  objects  and  on  paper.  Rosenau  says  that 
bedding  may  harbor  the  infection  for  a  long  time.  Tidswell,^ 
experimenting  with  a  large  number  of  materials,  found  that 
plague  bacilli  dried  under  natural  conditions  lived  only 
from  3  to  4  days,  but  when  dried  slowly  on  muslin  they 
might  live  for  21  days.  The  colder  the  climate  the  greater 
is  the  chance  of  the  persistence  of  infection.  In  this  all  are 
agreed. 

Pus-forming  Bacteria. — The  pus-forming  bacteria  are  quite 
resistant  to  drying.     According  to  Germano,**  streptococcus 

1  Gotschlich,   cited  by  Kolle  and  Wassennan's  Handbuch   [etc.], 
Jena,  1903,  II,  496. 

*  Simpson,  Treatise  on  Plague,  Cambridge,  1905,  93. 
'  Verjbitski,  J.  Hyg.,  Cambridge,  1908,  203. 

*  Rosenau,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 
No.  4,  1901. 

6  Tidswell,  Report  on  Plague  in  Sydney,  J.  A.  Thompson,  1902,  67. 
^  Germane,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1897,  XXVI, 
66. 


IXFECTIOX  BY  FOMITES  195 

withstands  drying  for  a  month,  but  different  strains  have 
varying  degrees  of  resistance.  See  also  Heim^  and  Neisser,^ 
who  found  that  these  organisms  would  withstand  drying  for 
a  long  time.  Buckley^  could  keep  staphylococcus  ahve  for 
only  7  days  when  on  paper  in  the  air,  and  on  other  sub- 
stances and  under  different  conditions  for  varying  times,  up 
to  130  days  on  cotton  kept  in  a  desiccator. 

Cholera  Spirilla.  —  Germano^  in  a  number  of  experiments 
found  that  the  cholera  spirillum  in  dried  feces  lived  only  3 
days  and  in  other  experiments  onlj"  1  day.  He  also  cites  Zon- 
chello  as  reporting  that  it  is  among  the  least  resistant  bac- 
teria. Kitasato^  states  that  it  may  retain  its  virulence  up 
to  8  days,  but  that  it  may  die  sooner,  especially  when  dried  on 
glass.  Usually  it  lives  from  a  few  hours  up  to  4  days.  Koch 
and  Gaffky^  state  that  when  dried  on  glass  it  survives  only 
a  few  hours,  but  when  dried  on  fabrics  it  may  retain  its  viru- 
lence up  to  4  days.  Buckley^  found  that  cholera  germs  would 
survive  when  dried  in  the  air,  9  hours  on  cotton,  8  hours  on 
wood,  It  hours  on  glass,  and  5  hours  on  paper.  They  did 
not  survive  nearly  so  long  when  dried  in  a  desiccator.  This 
is  contrary  to  the  experience  of  others,  for  as  a  rule  bacteria 
live  much  longer  when  dried  in  a  desiccator  than  when  dried 
in  the  open  air  under  natural  conditions.  Gotschlich^  says 
that  cholera  germs  will  live  in  dejecta  dried  in  the  air  on 
clothing  for  30  days,  and  when  damp,  according  to  Karl- 
niski's  observations,  for  7  months.  He  considers  that  such  a 
long  life  is  exceptional,  and  that  generally  the  spirillum  dies 
in  a  few  days.    A  duration  of  only  a  few  days,  or  even  hours, 

'  Heim,  Ztsch.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1905,  L,  122. 
'  Neisser,  Ucber  Luftstaub-Infection,  Inaug.  Dis.,  Breslau,  1898. 
'  Buckley,  Pub.  Health,  Lond.,  1S96-97,  XIX,  290. 

*  Germano,    Ztschr.    f.    Hyg.    u.    Infectionskrankh.,    Leipz.,    1897, 
XXIV,  40.3. 

'-"  Kitasato,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1885,  V,  134. 

•  Koch,  Arb.  a.  d.  k.  Gesundsamtc,  Berl.,  laSfi,  I,  199. 

^  Gotschlich,  Kolle  and  Wasserman's  Ilandbuch  [etc.],  Jcua,  1902, 
I,  211. 


196         THE  SOURCES  AND  MODES  OF  INFECTION 

was  also  found  by  Gamaleia/  Hesse"  and  Koch  and 
Gaffky. 

Pneumococci.  —  The  pneumococcus  is  widely  distributed 
in  healthy  human  mouths,  and  the  opportunities  for  the 
direct  transference  of  fresh  secretion  are  so  numerous  that 
it  probably  is  of  no  importance  whether  this  organism  lives 
long  or  not.  Wood^  found  that  while  pulverized  sputum  lost 
its  virulence  in  a  few  hours  when  dried  in  mass,  it  might, 
under  favorable  conditions, retain  it  35  days.  Buerger*  recov- 
ered the  pneumococci  from  a  handkerchief  7  days  after  it  had 
been  in  use.  Germano^  and  some  others  claim  a  consider- 
ably greater  resistance.  Germano  kept  it  alive  in  dust  for 
140  days,  but  the  tendency  of  later  observers  is  to  consider 
it  a  much  feebler  organism. 

Influenza  Bacilli.  —  According  to  Pfeiffer,"  the  influenza 
bacillus  retains  its  vitality  when  dried  in  sputum  for  36  to  40 
hours.  When  dried  on  a  cover  glass  and  kept  at  37°  C.,  it 
survives  for  only  2  hours,  and  when  kept  at  room  temperature 
for  from  8  to  20  hours. 

Meningococci.  —  The  evidence  in  regard  to  the  germ  of 
cerebro-spinal  meningitis  appears  to  be  somewhat  conflicting. 
Germano  and  Neisser  claim  considerable  resistance  for  it,  as 
also  does  Jaeger.^  Germano  said  it  would  live  for  80  to  90 
days,  but  it  is  said  that  he  did  not  work  with  the  true  menin- 
gococcus.* More  careful  and  recent  observers  do  not  find  it 
so  resistant.     Councilman^  found  that  it  would  live  when  dry 

'  Gamaleia,  Deutsche  med.  Wchnschr.,  1893,  XIX,  1350. 

*  Hesse,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1893,  XIV,  30. 
3  Wood,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  592. 

'  Buerger,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  518. 
^  Germano,  Ztschr. f .  Hyg. u. Infectionskrankh.,  Leipz.,  1897, XXVI, 66. 
'^  Pfeiffer,  Nothnagel's  Encycl.  Pract.  Med.,  Phila.  and  Lond.,  Influ- 
enza, 1895,  584. 

'  Jaeger,  Med.  Ivlin.,  Berl.,  1905,  I,  990,  1011. 
"  Arkwright,  J.  Hyg.,  Cambridge,  1907,  VII,  193. 

*  Special  Report  on  Cerebro-spinal  Meningitis,  Mass.  St.  Bd. 
Health,  1898,  78. 


INFECTION   BY  FO MITES  197 

in  a  dark  room  less  than  72  hours.  Albrecht  and  Ghon^ 
could  keep  it  only  24  hours  in  the  dark,  and  Bettencourt  and 
Franca^  less  than  9  hours.  Kache,^  Kutscher*  and  Fliigge^ 
had  similar  results,  and  Arkwright  ^  succeeded  in  keeping  the 
organism  alive  only  from  20  to  48  hours.  Lingelsheim '  says 
that  in  culture  media  it  dies  in  a  few  hours,  but  in  sputum 
it  may  be  kept  alive  for  5  days. 

Gonococci.  —  Among  the  least  resistant  bacteria  is  the 
gonococcus.  According  to  Schaffer  and  Steinschneider,*  it 
lives  only  a  few  hours  when  dried,  and  frequently  dies  as 
soon  as  thoroughly  dry.  Gonorrheal  pus  dried  on  a 
towel  lost  its  virulence  in  36  hours,  and  dried  on  linen  it 
lived  only  a  few  hours. ^  I  have  been  unable  to  find  any 
experimental  evidence  as  to  the  resistance  of  the  spirochete 
of  syphilis. 

Bacteria  on  Fomites.  —  Pathogenic  bacteria  have  fre- 
quently been  sought  for  on  various  articles  believed  to  be 
likely  to  be  the  means  of  transporting  disease,  but  with  the 
exception  of  the  spores  of  anthrax  and  tetanus  they  have 
rarely  been  found.  The  finding  of  anthrax  and  tetanus  spores 
has  already  been  referred  to.  Besides  the  places  mentioned, 
tetanus  germs  have  been  found  in  the  soil  in  various  places, 
in  the  dirt  filling  between  the  floors  of  houses'"  and  in  one 

'  Albrecht  and  Ghon,  Wien.  klin.  Wchnschr.,  1901,  XIV,  984. 
^  Bettencourt  and  Franca,  Ztsch.  f.  Hyg.  u.  Infectionskrankh.,  Leipz., 
1904,  XLVI,  463. 
'  Cited  by  Flugge. 

*  Kutscher,  Deutsche  med.  Wchnschr.,  1906,  XXXII,  1071. 

*  Flugge,  Klin.  Jahrb.,  Jena,  1905,  XV,  373. 

*  Arkwright,  J.  Hyg.,  Cambridge,  1907,  VII,  193. 

'  Lingelsheim,  Klin.  Jahrb.,  Jena,  190.',,  XV,  373;  Zt-schr.  f.  Hyg.  u. 
Infectionskrankh.,  Leipz.,  1908,  LIX,  4.57. 

'  Verhandl.  d.  IV  Kong.  d.  deutsch.  dermatol.  Gesellsch.,  Breslau, 
1904. 

*  Ullmann,  Wien.  med.  Blatter,  1897,  XX,  703  et  seq. 

'"  Heinzelmann,  Munchen  med.  Wchnschr.,  1891,  XXXVIII,  185, 
200. 


198         THE  SOURCES  AND  MODES  OF  INFECTION 

instance  in  a  house  where  there  had  been  a  death  from 
tetanus/ 

Distribution  of  Germs  of  Suppuration.  —  The  pus  organ- 
isms are  quite  resistant  to  drying,  and  if  they  were  not,  they 
are  so  widely  distributed,  being  found  constantly  on  the  skin 
and  mucous  surfaces  of  human  beings,  that  their  presence 
might  be  expected  wherever  human  beings  are  found.  They 
have  as  a  matter  of  fact  been  found  almost  wherever  sought, 
as  on  clothing,  books,  money,  instruments,  floors  and  wood- 
work, and  indeed  on  anything  that  is  touched  by  the  hand 
of  man. 

Diphtheria  Bacilli  on  Fomites.  —  Diphtheria  bacilli  have 
been  frequently  searched  for  on  all  kinds  of  objects  and  fre- 
quently found.  AbeP  and  Wesbrook^  found  them  on  toys, 
and  in  Abel's  case  it  was  86  days  after  infection.  Trevelyan* 
recovered  them  from  a  handkerchief  1 1  weeks  after  it  had  been 
used  by  a  diphtheria  patient.  Park^  took  cultures  which 
proved  positive  in  almost  every  instance,  from  dried  stains  on 
bedclothing  soiled  by  children  sick  with  diphtheria.  He  also 
found  the  bacilli  alive  in  a  piece  of  membrane  after  4  months. 
Wright  and  Emerson  ^  made  20  cultures  from  various  articles 
in  the  Boston  City  Hospital,  and  found  5  positive.  Of  these 
3  were  from  the  shoes,  1  from  the  hair  of  an  attendant,  and 

1  from  a  floor  brush.  Schumburg^  in  40  cultures  from  a 
room  occupied  by  a  diphtheria  patient  recovered  virulent 
bacilli  from  a  drinking  glass  and  the  handle  of  a  mirror.    In 

2  of  the  5  cultures  the  virulence  of  the  organism  was  low. 

^  Gotschlich,  Kolle  u.  Wasserman's  Handbuch  [etc.],  Jena,  1902, 1,  210. 

2  Abel,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig.,  Jena,  1892,  XIV, 
756. 

*  Wesbrook,  Wilson  and  McDaniel,  Am.  Pub.  Health  Ass.  Rep., 
1899,  XXV,  546. 

^  Trevelyan,  Lancet,  Lond.,  1900,  I,  1443. 

5  Park,  Med.  Rec,  N.  Y.,  1892,  XLII,  116. 

^  Wright  and  Emerson,  Centralbl.  f.  Bakteriol.  [etc.],  I  Abt.  Orig., 
Jena,  1894,  XVI,  412. 

'  Schumburg,  Ztschr.  f.  arztl.  Fortbild.,  Jena,  1905,  II,  567. 


INFECTION  BY  FO MITES  199 

Weichardt^  took  300  swabbings  from  various  things  in  a 
sick-room  and  250  from  other  parts  of  the  house,  and  found 
diphtheria  germs  3  times  on  o]:)jects  which  had  been  in  contact 
with  the  patient's  mouth.  HilP  took  532  swabbings  from  a 
room  occupied  by  a  diphtheria  patient,  and  obtained  4  posi- 
tive results,  all  of  which  were  from  objects  handled  by  the 
patient.  In  Providence  about  200  swabbings  taken  under 
similar  circumstances  showed  no  diphtheria  bacilli.  These 
last  three  observations  indicate  that  diphtheria  bacilli  are 
not  very  numerous,  even  on  objects  brought  into  close  con- 
tact with  the  patient.  Kober^  could  find  no  bacilh  on  the 
floor,  bed  linen,  etc.,  of  10  houses  in  which  there  had  been 
diphtheria,  and  he  states  that  Heymann  did  not  find  them 
in  the  H3'gienic  Institute  at  Breslau.  Klein  could  not  find 
them  on  telephones  in  London,^  and  Hill  in  Boston  "^  could 
not  find  them  on  24  mouthpieces  of  lung-testing  machines. 

Tubercle  Bacilli  on  Fomites.  —  While  the  tubercle  bacillus 
is  not  .<o  resistant  to  drying  as  was  formerly  thought,  it  is 
discharged  in  such  numbers  in  the  sputum  that  it  has  been 
found  outside  of  the  body  more  often  than  have  any  other 
organisms  except  the  pus-forming  bacteria.  Reference  to 
finding  it  in  dust  will  be  given  in  the  next  chapter.  When 
in  considerable  masses  of  sputum,  and  kept  damp,  the  bacillus 
will  survive  longer  than  when  mixed  with  dust.  Besides  on  the 
floors  and  various  articles  in  rooms,  the  bacillus  has  been 
found  in  l)ooks  which  were  in  use  for  some  years  in  a  circu- 
lating library."  Petersson^  examined  the  history  charts  kept 
by  the  bedside  of  tuberculous  patients  and  put  away  for 

1  Weichardt,  Jahresl).  u.  d.  Fortschr.  .  .  .  d.  path.  Mik.,  Baum- 
Rarten,  1900,  XVI,  197. 

'  Hill,  Am  Pub.  Hoalth  Ass.  Rep.,  1902,  XXVIII,  209. 

'  Kober,  Ztsrhr.  f.  Hyg.  u.  Infeotionskrankh.,  Leipz.,  1899,  XXXI, 449. 

*  Klein,  Abst.  .1.  Am.  M.  As.s.,  Chicago,  1905,  XLIV,  1866. 
»  Hill,  Rep.  Hd.  Health,  Bo-ston,  1906,  91. 

*  Mitulescu,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1903, 
XLIV,  397. 

'  Petersson,  Ztschr.  f.  klin.  Med.,  Berl.,  1907,  LXIII,  346. 


200         THE  SOURCES  AND  MODES  OF  INFECTION 

periods  varying  from  months  to  years.  He  found  by  micro- 
scopic examination  tubercle  bacilli  on  two  books  that  were 
kept  for  six  years.  Bissell  ^  washed  the  pockets  of  some  uni- 
forms that  had  been  used  by  soldiers  sick  with  consumption, 
and  obtained  two  positive  results  by  guinea-pig  inoculation. 
Friberger  ^  used  a  vacuum  cleaner  to  remove  the  dirt  from 
clothing  fresh  from  use  by  tuberculous  patients,  and  found 
virulent  bacilli  in  3  of  12  tests. 

Cholera  Spirilla.  —  Although  the  life  of  the  cholera  spiril- 
lum outside  of  the  body  appears  to  be  short,  usually  only  a 
few  days  and  often  less,  some  early  observers,  as  Babes,^  claim 
to  have  found  it  on  the  personal  effects  of  cholera  patients. 

Resistance  of  Protozoa.  —  There  is  no  theoretical  reason 
why  the  protozoan  blood  parasites  might  not,  in  a  spore-like, 
resistant  stage,  withstand  drying  and  remain  alive  for  some 
time  outside  of  the  body.  But  there  is  no  experimental  evi- 
dence to  show  that  in  any  of  the  well-known  protozoan  dis- 
eases such  spores  are  formed.  There  is  certainly  no  clinical 
evidence  to  show  that  such  diseases  are  ever  carried  on 
fomites,  and  for  malaria,  yellow  fever,  sleeping  sickness  and 
Texas  cattle  fever  there  is  convincing  evidence  that  they 
are  not  so  carried. 

Resistance  of  Vaccine  Virus.  —  With  two  exceptions,  prac- 
tically no  experimental  work  has  been  done  with  the  virus 
of  any  of  the  infectious  diseases,  a  specific  organism  for  which 
has  not  been  determined.  Vaccine  virus  has  an  extensive 
use,  and  it  is  desirable  to  store  it  and  transport  it  long  dis- 
tances, so  that  its  keeping  qualities  have  received  considerable 
attention.  When  the  infectious  material  dries  naturally  in 
the  crust  which  forms  from  the  vesicle,  it  retains  its  virulence 
for  a  considerable  time.    These  crusts  were  largely  used  in 

1  Bissell,  Med.  News,  N.  Y.,  1899,  LXXIV,  156. 

^  Friberger,  Ztschr.  f.  Tuberk.  u.  Heilstaltenw.,  Leipz.,  1908-09,  XIII, 
37. 

^  Shakespeare,  Report  on  Cholera  in  Europe  and  India,  U.  S.  Gov. 
Print.  Off.,  1890,  606. 


INFECTIOX  BY  FOMITES  201 

Providence  for  maintaining  the  Jennerian  strain  of  vaccine, 
which  was  used  in  the  health  department  for  nearly  fifty 
years.  The  crusts,  when  taken  from  the  arm  and  kept 
wrapped  in  paper  in  a  dark  place,  could  be  relied  upon  to 
retain  their  virulence  for  a  month,  and  often  did  retain  it 
longer.  When  kept  in  a  tightly  corked  bottle  in  a  refrigerator, 
they  will  generally  remain  virulent  over  6  months.  If  exposed 
to  light  and  air  and  varying  temperature,  the  virulence  may 
be  lost  in  less  than  a  month.  A  thin  layer  of  the  same  Ij^mph 
on  a  quill  does  not  remain  active  wh.en  exposed  to  the  air 
for  more  than  a  week  or  ten  days.  The  ivory  points  covered 
with  vaccine  matter,  which  were  so  much  used  a  few  years 
ago,  were  usually  guaranteed  to  keep  3  weeks,  and  often  did 
remain  virulent  a  month  or  more.  But  there  was  usually 
more  than  one  layer,  and  the  thickness  of  the  material  was 
further  increased  by  the  presence  of  blood  and  leucocytes. 
According  to  Seaton,^  dried  vaccine  matter  on  points  may 
keep  for  from  6  or  9  months  or  more,  and  he  quotes  Husband 
as  securing  successful  vaccinations  from  7  of  93  dried  points 
kept  for  periods  varying  from  6  to  30  months.  Vaccine  matter 
in  powder  also  has  been  kept  by  Warlomont  and  others  for 
several  months.^  Recently  Green  ^  has  kept  dried  pulverized 
vaccine  matter  in  sealed  tubes  for  periods  varying  from  20 
days  at  37°  C.  to  252  days  at  10-15°  C.  and  301  days  at 
4°  C.  Although  under  exceptional  circumstances  dried  vac- 
cine matter  may  be  kept  a  considerable  time,  it  requires  great 
care  and  often  results  in  failure.  Hence  early  in  the  nine- 
teenth century,  in  order  to  introduce  vaccination  into  her 
American  possessions,  the  Spanish  Government*  sent  out  a 
ship  with  a  number  of  children  on  board,  so  that  by  successive 
arm-to-arm  vaccinations  fresh  lymph  might  l)e  carried  across 
the  seas.    At  the  end  of  the  nineteenth  century,  when  Porto 

>  Seaton,  Handbook  of  Vaccination,  1868,  172. 

*  Warlomont,  Manual  of  Animal  Vaccination,  Phila.,  1886,  139. 
»  Green,  J.  Hyg.,  Cambridge,  1908,  VIII,  528. 

*  Life  of  Jenner,  Baron,  I,  606;  II,  78. 


202         THE  SOURCES  AND  MODES  OF  INFECTION 

Rico  came  under  the  control  of  the  United  States,  the  diffi- 
culty of  transporting  vaccine  virus  to  the  island  became  so 
great,  so  little  active  virus  surviving  even  this  short  voyage, 
that  it  was  necessary  to  establish  a  vaccine  farm  on  the  island. 
In  the  Philippine  Islands  it  was  found  to  be  necessary  to 
transport  the  virus  packed  in  ice  to  inland  villages.^ 

Resistance  of  Smallpox  Virus.— It  is  a  common  belief  that 
the  crusts  in  variola  are  infectious,  and  they  are  supposed  to 
have  been  used  at  times  in  the  practice  of  inoculation.  I  do 
not  remember  to  have  seen  any  evidence  of  this  till  I  came 
across  the  work  of  Brinckerhoff.^  He  refers  to  a  rather  limited 
literature,  and  details  his  own  experiments,  which  determined 
a  persistence  of  virulence  in  the  crusts  for  periods  of  from  22 
to  52  days,  and  in  one  instance  to  88  days. 

Comparative  Resistance.  —  Experiment  shows  that  some 
pathogenic  organisms,  like  those  of  gonorrhea  and  cerebro- 
spinal meningitis,  are  of  such  feeble  resistance  that  infection 
by  fomites,  as  ordinarily  understood,  is  in  these  diseases  highly 
improbable.  It  is  also  shown  that  certain  other  bacteria,  as 
those  of  diphtheria,  typhoid  fever  and  tuberculosis,  are  resist- 
ant enough  to  make  infection  by  fomites  very  possible.  But 
it  appears  that  all  known  pathogens,  except  those  having 
spores,  tend  to  die  off  quite  rapidly  outside  of  the  body,  and 
that  under  natural  conditions  it  is  rather  the  exception  for 
them  to  persist  for  any  great  length  of  time.  It  is  worth 
noting  that  the  typhoid  bacillus  is  more  resistant  than  any 
other  pathogenic  organism  referred  to.  Yet  we  hear  almost 
nothing  about  fomites  infection  in  that  disease.  Is  it  not 
because  attention  has  been  directed  to  other  sources  which 
have  been  believed  to  be  sufficient,  so  that  there  has  been 
little  temptation  to  assume  infection  by  fomites  ?  Infection 
by  fomites  has,  on  the  other  hand,  been  considered  of  much 
importance  in  cholera,  the  spirillum  of  which  is  far  less  resist- 
ant than  is  the  bacillus  of  typhoid  fever,  probably  because 

1  Rep.  Bd.  Health,  Philippine  Isl.,  1904-05,  23. 

'  Brlnckerhoff,  J.  Med.  Research,  Bost.,  1904,  XI,  284. 


INFECTION  BY  FOMITES  203 

in  the  absence  of  the  knowledge  of  carriers  which  we  now 
possess  the  world-wide  diffusion  of  this  disease  seemed  inex- 
plicable except  by  means  of  fomites. 

Experiments  with  Yellow  Fever.  —  With  a  few  notable 
exceptions,  little  experimental  work  has  been  done  to  deter- 
mine the  part  played  by  fomites  in  the  spread  of  disease. 
When  Reed,  Carroll  Lazear  and  Agramonte  proved  that  yel- 
low fever  is  transmitted  by  the  mosquito,  it  still  remained 
uncertain  whether  it  might  not  also  be  carried  in  other  ways, 
and  sanitary  officials  were  generally  so  convinced  of  the  over- 
whelming evidence  of  the  great  part  pla3^ed  by  fomites,  that 
definite  proof  or  disproof  of  the  fact  was  earnestly  desired. 
The  complete  failure  of  the  commission  to  produce  the  disease 
in  human  beings  by  fomites  is  well  known,  and  their  experi- 
mental work  has  now  been  corroborated  by  abundant  clinical 
evidence  from  all  the  great  endemic  foci  of  this  disease.  In 
these  experiments,  non-immunes  were  confined  in  a  small 
room  for  a  number  of  daj's  in  close  contact  ^vith  bedding  and 
clothing  fresh  from  yellow-fever  cases,  most  of  which  was 
soiled  with  excreta  and  vomitus.'  The  experiments  were 
repeated  a  number  of  times,  but  in  no  instance  did  the  disease 
develop.  When  not  long  after  I  stood  in  one  of  those  dirty 
little  rooms  in  company  with  Dr.  Finlay  and  Dr.  Gorgas,  and 
saw  some  of  the  old  bedding  lying  in  the  corner,  I  realized 
as  never  before  how  very  much  greater  are  the  difficulties  in 
observation  than  in  experiment,  and  it  seemed  that  the  time 
had  come  when  the  prevailing  views  as  to  the  importance  of 
fomites  infection  in  other  diseases  than  yellow  fever  should 
be  seriously  reviewed. 

Observations  on  Plague.  —  In  another  disease,  bubonic 
plague,  ('xccptioualiy  l)rilliunt  work,  from  the  purely  epidemi- 
ological standpoint,  has  been  done  by  Thompson  in  Australia. 
It  is  true  enough  that  conditions  are  much  more  favorable  for 
observation  wlien  a  disease  first  invades  a  country  than  when 
it  has  become  as  widespread  as  plague  is  in  India,  but  in  no 
'  rhik.  M.  J.,  1900,  VI,  790. 


204         THE  SOURCES  AND  MODES  OF  INFECTION 

place  have  they  been  taken  advantage  of  as  they  were  in 
Sydney.  Thompson  ^  showed  conclusively  that  rat  plague 
preceded  human  plague,  that  the  flea  was  the  intermediary 
between  rat  and  man,  and  that  in  New  South  Wales,  at  least, 
fomites  had  no  part  in  the  diffusion  of  the  disease.  These 
observations  have  been  confirmed  in  other  parts  of  Australia.^ 
Experiments  with  Plague.  —  The  present  English  Plague 
Commission  have,  by  their  ingenious  and  painstaking  ex- 
periments and  observations  in  India,  confirmed  Thompson's 
work.  Reference  will  be  made  in  another  chapter  to  the 
experiments  on  the  transmission  of  the  disease  by  the  air,  in 
which  they  definitely  proved  that  aerial  infection  does  not 
take  place.  They  also  studied  experimentally  the  conditions 
of  house  infection,  and  their  work  is  among  the  best  planned 
and  executed  and  the  most  convincing  of  any  that  has  ever 
been  attempted  for  any  disease.  Besides  much  other  work, 
they  placed  guinea  pigs  in  the  houses  of  an  Indian  village 
just  vacated  by  the  inhabitants  because  of  plague,  thus  sub- 
stituting an  experimental  population  under  control  for  the 
normal  human  population.^  The  results  were  in  every  way 
in  accord  with  the  view  that  plague  is  primarily  a  rat  disease, 
and  is  transmitted  from  rats  to  man,  or  to  other  animals,  by 
means  of  fleas.  In  these  and  in  similar  less  extensive  experi- 
ments *  there  was  evidence  to  show  that  the  animals  could 
not  contract  the  disease  from  the  dwellings  themselves.  To 
test  more  definitely  the  possibility  of  transmission  by  fomites 
other  experiments  were  made.  The  floors  of  houses  were 
soaked  with  cultures  of  the  bacilli,  and  guinea  pigs  placed 
upon  them.  Of  24  exposed  during  the  first  hour  after  in- 
fection 4  died;  of  12  exposed  up  to  six  hours  4  died;  but 
during  all  this  interval  pools  of  the  culture  were  upon  the 
floor.      Of   24  animals  exposed  after   twelve  hours  only   1 

1  Thompson,  J.  Hyg.,  Cambridge,  1906,  VI,  537. 

^  Ham,  Rep.  on  Plague  in  Queensland,  1900-07,  Brisbane,  1907. 

'  J.  Hyg.,  Cambridge,  1907,  VH,  799-875. 

*  J.  Hyg.,  Cambridge,  1906,  VI,  450-482. 


INFECTION  BY  FOMITES  205 

succumbed.  Guinea  pigs  were  also  allowed  to  run  freely 
about  hospital  wards  in  which  cases  of  bubonic  plague  were 
being  treated,  and  15  were  confined  in  a  room  with  freshly 
soiled  bedding,  which  was  renewed  every  day  for  six  weeks. 
In  none  of  the  animals  did  the  disease  develop.  Again  (p. 
887),  clothing  from  infected  houses,  removed  without  precau- 
tions to  prevent  the  transport  of  fleas,  was  placed  in  cages 
containing  26  guinea  pigs,  1  of  which  died  of  the  plague.  A 
few  fleas  which  had  been  brought  in  the  clothing  were  found  in 
the  cages.  It  seems  to  be  quite  clear  from  these  experiments 
that  while  infection  by  fomites  is  possible,  it  is  probable  only 
when  the  infection  is  exceedingly  gross  and  the  contact  is  inti- 
mate, as  in  the  case  of  the  infected  floors  referred  to  above;  or 
it  may  also  be  possible  when  infected  fleas  are  transported  in 
the  goods.    How  common  this  is  has  not  yet  been  determined. 

Tuberculosis.  —  I  know  of  no  other  diseases  in  which  seri- 
ous experimental  work  has  been  done  to  determine  the  part 
played  by  fomites  in  their  diffusion.  It  is  particularly  remark- 
able that  tuberculosis  has  not  been  thus  critically  studied. 
Every  one  has  been  calling  for  room  disinfection  as  a  powerful 
means  of  combating  this  disease,  yet  it  does  not  seem  to  have 
occurred  to  any  one  to  place  susceptible  animals  in  a  series  of 
supposedly  infected  rooms  (as  was  done  in  the  case  of  plague 
in  India)  to  determine  if  possible  how  great  the  danger  from 
room  infection  really  is. 

Disinfection  of  Little  Value.  —  From  a  consideration  of  the 
facts  presented  in  this  chapter  the  writer  became  convinced 
some  time  since  that  the  danger  from  fomites  infection  is 
for  most  diseases  very  much  less  than  is  generally  believed. 
In  diphtheria  particularly  it  appeared  that  little  if  any  sick- 
ness could  be  due  to  infection  remaining  about  the  house  or 
its  contents  after  the  termination  of  isolation.  As  isolation 
is  almost  invariably  terminated  without  any  reference  to  the 
presence  of  carriers  in  the  family,  it  appeared  to  be  absurd 
to  disinfect  the  material  things  in  the  house  when  in  all  prob- 
ability some  carrier  was  still  growing  the  bacilli.    Hence  in 


206        THE  SOURCES  AND  MODES  OF  INFECTION 


March,  1905,  terminal  disinfection  was  abandoned  in  Provi- 
dence, except  in  those  very  few  instances  in  which  the  family- 
was  willing  to  wait  for  two  successive  negative  throat  and 
nose  cultures  from  each  of  its  members.  The  attempt  was 
thus  made  to  test  the  importance  of  fomites  infection  by 
abandoning  disinfection  and  noting  any  change  that  might 
occur  in  the  prevalence  or  distribution  of  the  disease.  One 
obvious  way  of  testing  the  influence  of  disinfection  is  to  com- 
pare the  recurrence  of  the  disease  after  disinfection  with  the 
amount  which  occurred  after  the  warning  placard  was  re- 
moved without  disinfection.  The  following  shows  the  recur- 
rences in  the  two  classes  of  cases. 

The  number  of  recurrences  after  disinfection,  the  number 
of  infected  families  and  the  ratio  between  th^'  two,  during 
the  years  1902  and  1905,  was  as  follows: 


Year. 

Infected 
Families. 

Recurrences. 

Ratio. 

1902 

1903 

1904 

1905 

Total 

358 

453 

559 

87 

1457 

6 
7 

10 
2 

25 

1.67 
1.54 

1.78 
2.30 
1.71 

The  number  of  recurrences  since  February,  1905,  where 
there  was  no  disinfection  and  the  ratio  to  infected  families 
where  there  was  no  disinfection  are  as  follows: 


Year. 

Infected 
Families. 

Recurrences. 

Ratio. 

1905 

1906 

1907 

1908 

1909       

258 
259 
343 
687 
472 
2019 

4 

4 

7 

17 

10 

42 

1.55 
1.55 
2.04 
2.34 
2.12 
2.08 

Total 

INFECTION  BY  FOMITES  207 

The  period  from  1902  only  is  taken,  because  previous  to  that 
time  the  duration  of  isolation  was  somewhat  longer,  but  there 
has  been  no  change  since.  Very  few  health  officers  keep  any 
record  of  the  recurrences  in  diphtheria  and  other  infectious 
diseases,  but  it  is  interesting  to  note  that  in  Baltimore,  where 
terminal  disinfection  is  practiced  in  an  unusually  thorough 
manner,  and  is  in  a  large  majority  of  cases  tested  for  its  effi- 
ciency, recurrences  in  diphtheria  occur  in  1.89  per  cent  of  the 
cases. 

Again,  it  ma}'  be  objected  that  recurrence  in  the  family  is 
no  criterion  of  the  infection  of  the  house,  for  it  may  be  that 
the  family  is  largely  immune.  This  would  certainly  be  much 
less  true  of  those  members  of  the  family  who  went  away  dur- 
ing the  sickness.  Of  510  minors  who  thus  returned  to  the  non- 
disinfected  house  only  1  was  taken  sick.  So  too  if  terminal 
disinfection  is  such  an  important  matter,  its  neglect  should  be 
followed  by  an  increase  in  the  disease.  As  a  matter  of  fact, 
after  disinfection  was  abolished  diphtheria  diminished,  until 
at  one  time  in  the  following  August  there  was  not  a  single 
reported  case  in  the  city.  Again  in  August,  1908,  the  disease 
was  reduced  to  a  single  recognized  case.  There  has  been  a 
marked  increase  since,  common  to  many  parts  of  New  Eng- 
land, and  the  excess  in  Boston,  where  disinfection  is  practiced, 
has  been  greater  than  in  Providence.  Still  another  test  of  the 
danger  from  the  omission  of  disinfection  is  the  extension  of 
the  disea.se  to  other  families  in  the  same  house.  Of  over  1200 
such  families  only  10  were  invaded  by  the  disca.se  within  two 
months  after  the  termination  of  isolation  in  the  non-disin- 
fected apartment.  It  may  be  suggested  that  though  no  offi- 
cial disinfection  was  practiced,  the  houses  were  perhaps 
tiioroughly  cleansed  by  the  occupants.  I  must  confess  that 
I  hoped  that  the  abandonment  of  official  disinfection  would 
cause  people  to  do  more  cleansing  for  themselves,  but  there 
has  thus  far  been  little  improvement,  and  as  a  large  part  of 
our  diphtheria  occurs  among  poor  and  ignorant  people,  many 
of  whom  are  recent  immigrants,  house  cleaning  by  the  family 


208       THE  SOURCES  AND  MODES  OF  INFECTION 

can  scarcely  be  expected  to  be  very  efficient  at  present.  It 
appears,  then,  that  this  experiment  shows  that  house  infection 
in  diphtheria  is  in  Providence  a  neghgible  factor  in  the  dis- 
semination of  the  disease. 

French  Views  on  Disinfection.  —  Recently, ^  at  a  discussion 
in  Paris,  Comby,  Courmont  and  Lemoine  took  the  ground 
that  the  active  disinfection  which  has  been  insisted  on  in  that 
city  in  recent  years  has  not  reduced  the  mortality  from  scarlet 
fever,  diphtheria  or  measles,  for  which  diseases  it  is  required. 
Comby  ^  is  emphatic  in  his  contention  that  it  is  persons,  not 
things,  that  are  the  bearers  of  contagion.  The  same  position 
was  taken  by  Semaine  Medicale  for  February  14,  1906. 
Lemoine  ^  has  found  disinfection  not  so  essential  as  has  been 
claimed.  At  the  hospital  at  Val  de  Grace  certain  rooms  were 
used  for  isolating  single  cases  of  contagious  disease.  There 
was  often  such  demand  for  their  use  that  cases  of  different 
diseases  quickly  succeeded  one  another,  sometimes  without 
any  disinfection  and  often  with  slight  disinfection  by  washing 
the  walls  as  high  as  could  be  reached.  Sixty -five  cases  of 
scarlet  fever,  41  of  measles,  25  of  mumps,  31  of  diphtheria, 
4  of  smallpox,  1  of  chicken  pox  and  136  of  other  diseases  are 
reported  as  rapidly  succeeding  one  another  in  these  rooms. 
One  case  of  measles  and  4  of  scarlet  fever  developed  in  the 
rooms.  Often  it  was  necessary  to  shift  entire  wards  of  twenty 
to  thirty  beds,  with  only  a  slight  attempt  at  disinfection.  This 
was  done  a  good  many  times  during  nine  years  without  bad 
results. 

When  official  disinfection  after  measles  was  temporarily 
suspended  in  New  York  from  January  10,  1908,  to  March  1, 
neither  the  suspension  nor  the  resumption  of  the  practice 
appeared  to  have  any  effect  on  the  epidemic  curve.  Rich- 
ards *  does  not  consider  disinfection  of  the  room  necessary, 

1  Bull,  et  mem.  Soc.  med.  d.  hop.  de  Par.,  1909,  n.  s.,  XXVII,  585. 

»  Comby,  Presse  med.,  Paris,  1909,  XXVII,  249. 

'  Lemoine,  Rev.  d'hyg.,  1907,  XXIX,  1057. 

*  Richards,  Pub.  Health,  Lond.,  1909,  XXIII,  42. 


INFECTION  BY  FOMITES  209 

provided  the  floors  are  washed  and  things  which  come  in 
contact  with  the  patient  are  cleansed  and  disinfected. 

School  Disinfection.  —  When  a  number  of  cases  of  scarlet 
fever  or  diphtheria  develop  in  a  school,  the  pubhc  is  inclined 
to  consider  room  infection  the  source  and  to  demand  "dis- 
infection." This  subject  has  lately,  perhaps  owing  in  part 
to  the  efforts  of  sellers  of  disinfectants,  been  much  discussed 
in  England,  but  fortunately  the  leading  ofl&cials  refuse  to  be 
influenced  by  public  clamor.  Among  others,  Kerr^  has  clearly 
set  forth  the  reasons  why  the  room  can  rarely  be  at  fault  in 
school  outbreaks  of  the  contagious  diseases. 

Disinfection  Unnecessary  in  Other  Diseases. — Owing  to  the 
similarity  between  the  two  diseases  it  seems  to  me  that  there 
is  probably  no  more  value  in  disinfection  after  scarlet  fever 
than  there  is  in  disinfection  after  diphtheria.  In  fact  in  any 
disease  which  is  widely  distributed,  and  in  which  there  is  ample 
opportunity  for  extension  from  refild  cases,  from  carriers,  from 
cases  in  the  early  stages,  and  from  convalescents,  the  absolute 
disinfection  of  all  possible  fomites  at  the  assumed  termina- 
tion of  the  sickness  will  probably  have  no  influence  in  check- 
ing the  disease.  Thus  I  can  see  no  use  in  disinfecting  after 
measles,  whooping  cough,  influenza,  pneumonia  or  cerebro- 
spinal meningitis,  and  I  think  that  this  view  is  held  by  the 
majority  of  our  health  officers  and  epidemiologists.  Disin- 
fection after  diphtheria  is  al)surd  unless  it  be  shown  by  two 
or  three  negative  cultures  that  none  of  the  family  are  still 
growing  the  bacilli.  Disinfection  after  cerebro-spinal  menin- 
gitis is  also  absurd,  as  the  meningococcus  lives  only  a  few 
hours,  and  carriers  are  almost  the  sole  means  by  which  this 
disease  is  spread.  Much  disinfection  after  tuberculosis  is  also 
without  reason.  If  a  patient  has  been  living  with  his  family 
and  taking  no  precautions,  certainly  no  amount  of  terminal 
disinfection  will  atone  for  long-continued  sanitary  sin.  If 
precautions  are  taken,  the  phthisiologists  tell  us  that  there 
is  no  danger  in  living  with  the  patient,  and  if  so,  certainly 
»  Kerr,  Pub.  Health,  Lond.,  1909,  XXIII,  49. 


210        THE  SOURCES  AND  MODES  OF  INFECTION 

there  can  be  no  possible  danger  in  living  in  his  house  after 
he  is  dead.  The  only  occasion  for  disinfection  after  consump- 
tion, then,  is  when  the  apartments  of  a  careless  patient  are  to 
be  occupied  by  another  family,  and,  after  all,  we  have  no  evi- 
dence to  show  how  much  danger  there  is  even  then.  Yet 
many  health  officers  make  disinfection  after  every  death  from 
consumption  the  first  and  often  the  only  measure  taken  to 
restrict  tuberculosis. 

When  Terminal  Disinfection  is  Desirable.  —  When  a  new 
or  rare  disease  invades  a  locality,  it  may  at  times  be  desirable 
to  take  extraorclinarj^  precautions  to  prevent  its  extension, 
which  would  be  entirely  useless  if  the  disease  were  estab- 
lished. This,  it  is  true,  is  not  the  popular  or  legal  way  of 
regarding  preventive  measures,  but  it  is  the  scientific  one. 
If  a  case  of  smallpox  should  occur  in  Providence,  which  has 
been  free  from  it  for  four  years,  it  would  be  worth  while, 
perhaps,  to  expend  considerable  time  and  money  in  disinfec- 
tion, even  though  the  chance  of  infection  from  the  room  or 
goods  might  not  be  one  in  a  thousand.  But  if  there  were 
hundreds  of  cases  of  measles  in  the  city,  it  would  be  folly  to 
go  to  the  same  trouble  and  expense  for  each  case,  even  if  the 
chance  of  infection  were  ten  times  as  great.  A  spark  in  the 
dry  grass  should  be  stamped  out  at  any  cost,  but  it  is  useless 
to  waste  time  in  extinguishing  the  smoldering  flames  left  here 
and  there  as  the  line  of  fire  is  sweeping  across  the  prairie. 

Objections  to  Disinfection.  —  There  are  several  objections 
to  the  present  practice  of  terminal  disinfection.  One  is  that 
it  only  partially  disinfects.  If  disinfection  is  to  be  honestly 
and  efficiently  applied,  methods  must  be  changed.  But  even 
as  now  practiced,  disinfection  is  expensive.  Many  cities  em- 
ploy disinfectors,  with  horses  and  apparatus,  while  their  labo- 
ratory languishes,  their  medical  inspection  is  poor  and  their 
diphtheria  patients  must  secure  antitoxin  as  best  they  can. 
Another  serious  objection  to  routine  terminal  disinfection  is 
that  it  misleads  the  public.  They  are  given  a  false  sense  of 
security,  and  they  are  encouraged  in  the  old  belief  that  it  is 


INFECTION  BY  FOMITES  211 

things,  not  persons,  which  are  dangerous.  We  can  never  suc- 
cessfully preach  the  truth  about  carriers,  or  teach  the  neces- 
sity for  stricter  personal  cleanhness,  so  long  as  we  continue 
to  make  so  much  of  a  fetish  of  the  practice  of  disinfection. 

Cleanliness  versus  Disinfection.  —  I  am  here  referring  to 
terminal  disinfection,  which  is  often  only  a  fumigation,  or 
smell-producing  process.  The  continued  practice  of  cleanli- 
ness all  through  the  sickness,  and  indeed  at  all  times,  by 
which  the  transference  of  fresh  infective  material  may  be  pre- 
vented, is  another  matter,  the  value  of  which  was  considered 
in  the  preceding  chapter. 

Conclusions.  —  It  seems  to  me,  in  view  of  the  considera- 
tions here  presented,  that  we  are  justified  in  concluding  that, 

1.  There  is  no  good  epidemiological  evidence  that  any 
diseases  except  those  due  to  spore-forming  bacteria  are  to  any 
great  extent  transmitted  by  fomites. 

2.  Judging  from  our  experience  with  yellow  fever  most  of 
the  alleged  evidence  of  infection  by  fomites  is  not  to  be  relied 
upon. 

3.  Even  if  all  the  alleged  fomites  infection  is  real,  only  a 
very  small  part  of  contagious  disease  is  traceable  to  this 
source. 

4.  The  theory  of  fomites  infection  was  an  a  priori  not  an 
a  -posteriori  theory,  and  is  no  longer  demanded. 

5.  Other  modes  of  transmission  so  much  more  satisfac- 
torily account  for  the  spread  of  disease,  that  there  seems  to 
be  really  little  opportunity  for  infection  by  fomites. 

6.  Laboratory  investigation  shows  that  fomites  infection 
with  spore-forming  bacteria  is  common;  that  such  infection 
in  typhoid  fever,  tuberculosis,  diphtheria  and  with  other  resist- 
ant organisms  doubtless  sometimes  takes  place;  that  it  is 
possible  in  cholera  and  plague,  while  such  infection  in  gonor- 
rhea, influenza,  cerebro-spinal  meningitis  and  pneumonia 
must  be  practically  impossible. 

7.  Experiment  and  epidemiological  observation  have  dem- 
onstrated that  fomites   infection   is    practically  impossible 


212        THE  SOURCES  AND  MODES  OF  INFECTION 

in  yellow  fever  and  is  probably  so  in  the  other  insect-borne 
diseases. 

8.  Experiment  and  observation  show  that  fomites  are  of 
little  moment  in  the  diffusion  of  bubonic  plague,  and  of  no 
moment  in  the  extension  of  Mediterranean  fever,  both  for- 
merly believed  to  be  spread  in  this  way. 

9.  Observations  made  in  Providence  indicate  that  fomites 
infection  is  of  no  practical  importance  in  the  diffusion  of  diph- 
theria. 

Finally,  it  may  be  affirmed  that  the  evidence  has  been 
rapidly  accumulating  that  fomites  infection  is  of  very  much 
less  importance  than  was  formerly  believed. 


CHAPTER  VI. 

INFECTION    BY    AIR. 

Reasons  for  Former  Belief.  —  From  time  immemorial  the 
air  has  been  considered  the  chief  vehicle  of  infection.  This 
was  but  natural,  for  until  recently  the  virus  of  the  infectious 
diseases  was  believed  to  be  gaseous,  or  at  least  readily  dif- 
fusible, and  readily  borne  by  air  currents.  The  infective 
material  was  supposed  to  be  given  off  in  the  expired  breath, 
and  to  emanate  from  the  surface  of  the  body  and  from  moist 
soil  and  decomposing  matter  of  all  kinds.  Contagious  dis- 
eases were  known  to  arise  without  any  apparent  connection 
with  other  cases,  and  what  could  be  more  natural  than  to 
assume  that  the  invisible,  imponderable  materies  morhi  is 
mixed  with  and  carried  by  the  air?  Moreover  one  of  the 
most  widespread  and  best  kno\vn  diseases,  malaria,  was 
shown  by  a  great  mass  of  clinical  evidence  to  be  an  air-borne 
disease,  and  yellow  fever,  another  infectious  disease  of  great 
importance,  was  also  on  good  grounds  believed  to  be  trans- 
mitted in  the  same  manner.  What  seemed  to  be  well  estab- 
lished for  these  two  diseases  was  assumed  on  much  more 
slender  evidence  to  be  true  of  most,  if  not  all,  the  infectious 
diseases.  It  is  true  in  a  certain  sense  that  the  two  diseases 
just  mentioned  are  air-borne,  that  is,  they  are  transmitted  by 
small  insects,  which  "  diffuse,"  as  it  were,  from  their  breeding 
places  and  are  readily  wafted  by  air  currents.  It  is  not  in 
this  sense  that  the  term  air-borne  is  used  in  this  chapter,  but 
the  inquiry  here  made  is  whether  the  virus  of  the  infectious 
diseases  is  borne  by  the  air,  either  free  or  attached  to  small 
particles  of  inanimate  matter. 

Then,  again,  the  first  symptoms  of  measles,  and  often  of 
influenza,  are  connected  with  the  nose,  diphtheria  appears  to 
be  a  throat  disease,  while  consumption  and  pneumonia  infect 

213 


214       THE  SOURCES  AND  MODES  OF  INFECTION 

the  lungs.  What  is  more  natural  than  to  assume  that  the  air 
which  bathes  these  parts  is  the  vehicle  of  infection  ?  But  since 
it  has  been  shown  that  the  pneumococcus  is  constantly  found 
in  the  blood  in  pneumonia,  and  has  been  demonstrated  before 
the  initial  chill,  and  since  tubercle  bacilli  readily  reach  the  lungs 
through  the  circulation,  the  force  of  this  argument  is  lost. 

Omitting  the  insect-borne  diseases,  let  us  see  first  what 
epidemiological  evidence  there  is  that  the  contagious  diseases 
are  air-borne. 

Smallpox  Air-borne  from  Hospitals.  —  Smallpox  is  be- 
lieved to  be  more  widely  air-borne  than  is  any  other  disease. 
The  modern  doctrine  of  the  aerial  transmission  of  smallpox 
received  its  greatest  support  from  the  investigations  of  Power  ^ 
in  18S1  concerning  the  conditions  about  the  Fulham  Hospital 
in  London.  That  smallpox  could  be  carried  by  the  air  long 
distances  had  been  claimed  by  many  before  that  time,  for 
Dr.  Waterhouse  of  Cambridge,  more  than  one  hundred  years 
ago,  believed  the  disease  had  been  wafted  across  from  Boston 
to  Charlestown,  though  later  he  was  inclined  to  deny  this 
mode  of  transmission.  Power  showed  that  smallpox  had  not 
prevailed  to  any  extent  in  the  vicinity  of  the  Fulham  Hospital 
before  the  hospital  was  opened,  and  that  on  a  number  of  occa- 
sions soon  after  it  was  occupied  by  a  considerable  number  of 
patients  the  disease  began  to  develop  in  the  neighborhood. 
Furthermore  he  showed  that  there  was  a  progressive  decrease 
in  the  amount  of  smallpox  as  the  distance  from  the  hospital 
increased,  the  alleged  influence  of  the  hospital  extending  to 
at  least  one  mile.  It  was  furthermore  shown  by  the  doctor 
that  this  distribution  of  the  disease  was  uniform  in  every 
direction  from  the  hospital,  that  is,  in  every  quadrant  of  the 
circle  surrounding  it.  Later  investigations  at  this  hospital 
yielded  similar  data.^  Smallpox  almost  always  developed 
in  the  vicinity  whenever  the  hospital  was  occupied  by  from 

1  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  Lond.,  1880-81,  X,  Supl.  302. 

2  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  Lond.,  1884-85,  XIV,  55,  1885-86, 
XV,  111. 


INFECTION  BY  AIR  215 

eighty  to  one  hundred  acute  cases.  But  on  one  occasion,  at 
least,  there  was  no  outbreak  even  when  the  hospital  was  fully 
occupied.  The  conclusion  was  that  when  a  considerable 
number,  eighty  to  one  hundred,  acute  cases  of  smallpox  are 
gathered  in  a  hospital,  there  is  great  danger  that  the  virus 
of  the  disease  will  be  carried  by  the  air  a  mile  or  more  from 
the  hospital  in  quantity  suflScient  to  infect  persons  at  that 
distance.  Powers  considered  that  the  hospital  was  thus  the 
focus  of  infection  on  one  occasion  when  there  were  only 
twenty  patients,  and  at  another  time  when  there  were  only 
nine,  of  which  five  were  acute.  It  was  thought,  from  a  study 
of  the  conditions  at  the  time  of  the  outbreak,  that  the  dis- 
semination was  favored  by  still,  damp  weather.  A  somewhat 
similar  though  not  generally  so  well  defined  or  niceh^  graded 
distribution  of  smallpox  around  hospitals  was  believed  by 
many  to  have  been  demonstrated  in  the  cases  of  theHomerton, 
Deptford,  and  Hempstead  hospitals.  It  was  natural  that 
twenty-five  years  ago,  when  knowledge  of  modes  of  infection 
was  far  more  vague  than  at  the  present  time,  and  with  such 
evidence  at  hand,  the  officers  of  the  Local  Government  Board 
should  have  been  firmly  convinced  of  the  importance  of  aerial 
transmission  in  the  spread  of  smallpox,  and  that  this  opinion 
should  have  been  shared  by  many  medical  officers  of  health. 
Subsequent  to  the  investigations  referred  to  above,  outbreaks 
due  to  the  spread  of  this  disease  from  hospitals  are  said  to 
have  occurred,  among  other  places,  at  West  Ham,  1884-85,^ 
Nottingham,  1887-88,"  Oldham,  1888  and  1892,"  Warrington, 
1892-93,"  Bradford,  1893,'  Liverpool,  1902-03,"  and  in  Gates- 

1  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  Lond.,  1886-87,  XVI,  97. 

^  Whitelegge,  Practitioner,  Ix)nd.,  1888,  XLI,  65. 

'  Report  on  the  Health  of  Oldham,  1892,  by  Niven;  also  Niven,Pub. 
Health,  1802-93,  V,  321,  366. 

*  (lornall,  Rop.  on  the  Epidemic  of  Smallpox  in  the  years  1892-93 
in  Warrington,  188"),  HI. 

»  Evans,  Brit.  M.  J.,  Ix)nd.,  1894,  II,  356. 

«  Recce,  Special  Rep.  Loc.  Gov.  Bd.,  Lond.,  No.  208.  1905,  Smallpox 
in  Liverpool. 


216        THE  SOURCES  AND  MODES  OF  INFECTION 

head  and  Felling,  1903-04. ^  In  Glasgow^  Chalmers  states 
that  smallpox  seemed  to  develop  around  the  hospital  when 
it  contained  many  patients,  but  that  this  did  not  invariably 
occur.  When  the  hospital  was  removed  to  another  location, 
it  again  appeared  to  be  a  focus  of  disease.  Much  has  been 
made  of  the  alleged  aerial  transmission  of  smallpox  from  the 
ships  lying  in  the  Thames  below  London  and  used  for  the 
reception  of  cases  of  that  disease  from  the  metropolis.  Bu- 
chanan^ and  Thresh*  attempt  to  show  that  after  the  ships 
were  brought  into  use  the  disease  was  carried  by  the  air  to 
the  Essex  shore  at  Purfleet  and  West  Thurrocks  in  the  Orsett 
Union.  It  is  true  enough  that  the  incidence  of  the  disease 
was  very  great  in  these  districts,  but  it  is  difficult  to  under- 
stand why  it  is  not  as  well  explained  by  contact  infection,  as 
were  hundreds  of  similar  outbreaks  in  England  and  the  United 
States.  The  chief  evidence  on  which  the  theory  of  aerial 
infection  is  based  is  the  existence  around  the  hospital,  in 
every  quadrant,  of  a  graduated  incidence  of  the  disease.  No 
such  evidence  is  presented  in  this  instance,  and  the  area  of 
infection  attributed  to  the  ships  lies  only  in  one  direction 
from  them.  Smallpox  appeared  on  the  shore  nearest  the 
ships,  and  then  gradually  extended  to  a  distance  of  two  or 
three  miles.  This  sort  of  extension  is  just  what  would  be 
expected  in  contact  outbreaks.  If  air-borne,  the  near  and 
distant  communities  should  have  been  affected  at  the  same 
time.  It  was  claimed  by  Dr.  Thresh  that  the  influence  of 
the  ships  could  be  noted  at  a  distance  of  four  or  five  miles. 
It  was  also  claimed  that  several  vessels  anchored  near  the 
hospital  ships  developed  smallpox  twelve  days  later.  That 
ships  leaving  London  during  the  period  of  the  extensive  out- 

1  Buchanan,  Special  Rep.  Loc.  Gov.  Bd.,  Lond.,  Smallpox  in  Gates- 
head and  Felling,  1904. 

»  J.  Royal  San.  Inst.,  1905,  XXVI,  212,  and  Tr.  Epidemiol.  Soc, 
Lond.,  1904-05,  n.  s.,  XXIV,  151,  244. 

'  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  Lond.,  1902-03,  XXXII,  81. 

*  Thresh,  Tr.  Epidemiol.  Soc,  Lond.,  1902,  n.  s.,  XXI,  101. 


INFECTION  BY  AIR  217 

break  in  that  city  should  occasionally  carry  smallpox  with  them 
is  not  remarkable.  Finally  it  was  admitted  that  surrepti- 
tious communication  with  the  ships  occasionally  occurred. 

Aerial  Convection  Denied  by  Some.  —  Many  sanitary  offi- 
cials did  not,  and  do  not,  accept  these  conclusions,  and  nu- 
merous instances  are  given  where  the  disease  has  not  extended 
from  hospitals.  Thus  Renney-  says  that  in  1883-84  he  saw 
300  cases  of  smallpox  treated  in  wards  which  were  situated 
between  twenty  and  two  hundred  and  twenty-four  feet  of 
other  hospital  wards,  schools  and  houses,  without  any  exten- 
sion, though  only  the  school  was  protected  by  vaccination. 
At  another  time  he  saw  a  considerable  number  of  cases  cared 
for  wthout  harm  in  a  ward  from  forty  to  one  hundred  and 
thirty-eight  feet  from  other  occupied  buildings.  So  Wilson  at 
Rugby"  had  a  hospital  within  a  few  yards  of  a  much  fre- 
quented road  with  no  untoward  results.  At  many  other 
times  he  has  seen  smallpox  hospitals  maintained  in  close 
proximity  to  other  occupied  buildings  without  aerial  trans- 
mission resulting.  Boobbycr^  treated  20  cases  near  a  high- 
way where  a  thousand  workmen  passed  daily,  and  not  a  case 
was  contracted  from  them.  Ker'*  at  Edinburgh  had  a  small- 
pox hospital  in  connection  with  a  general  hospital,  and  close  to 
other  institutions,  and  with  a  population  of  3000  persons  liv- 
ing within  a  mile  circle.  There  were  only  4  cases  within  this 
circle,  of  which  2  were  known  to  be  contracted  elsewhere. 
Dr.  Thorne  Thome''  stated  that  in  two  instances  only  had 
he  seen  evidence  of  the  aerial  extension  of  smallpox  from  a 
hospital,  namely,  at  Maidstone  and  at  Stockton,  while  he  had 
seen  numerous  instances  where  there  was  no  extension, 
notably  at  Leeds  and  Nottingham. 

'  Renney,  Jour.  Roy.  San.  Inst.,  1905,  XXVI,  210. 

2  Wilson,  Brit.  M.  J.,  Lond.,  1905,  II,  630. 

3  Boobbyer,  Tr.  Epidemiol.  Soc,  Lond.,  1905,  n.  s.,  XXIV,  219. 
*  Ker,  Tr.  Epidemiol.  Soc,  Lond.,  1905,  n.  s.,  XXIV,  174. 

'  Thorne  Thorne,  Rep  Med.  Ofif.  Loc.  Gov.  Bd.,  Load.,  1880-81, 
X,  Supl.  40. 


218        THE  SOURCES  AND  MODES  OF  INFECTION 

At  Manchester  Niven^  reported  only  13  smallpox  cases 
out  of  a  population  of  over  40,000  living  within  a  half  mile 
to  a  mile  area  around  the  hospital  and  none  among  the  606 
persons  living  within  the  half-mile  circle.  Other  instances 
can  be  given  where  smallpox  hospitals  have  not  infected 
their  neighborhood,  and  these  facts  should  have  some  weight, 
though  according  to  the  advocates  of  the  theory  aerial  trans- 
mission is  to  be  expected  only  under  certain  conditions  of 
the  atmosphere.  There  is  not  much  evidence  bearing  upon 
this  subject  to  be  obtained  in  the  United  States,  partly 
because  smallpox  hospitals  have  been  much  more  rarely 
situated  in  thickly  populated  districts  and  partly  because 
less  attention  has  been  given  to  the  subject  here  than  in 
England. 

American  Evidence  against  Theory.  —  In  Philadelphia  it 
is  claimed  ^  that  the  hospital  has  been  the  source  of  smallpox 
in  its  neighborhood.  Thus  in  one  outbreak  in  the  municipal 
ward  in  which  the  hospital  was  situated  the  case  rate  was 
61  per  10,000,  nearly  twice  that  of  any  other  ward,  and  it 
decreased  as  the  distances  from  the  hospital  increased.  The 
same  conditions  were  noted  in  another  outbreak. 

In  Boston  in  1902-03  there  was  some  discussion  as  to 
whether  the  disease  spread  from  the  hospital,  which  was 
on  a  busy  street  and  near  many  occupied  buildings.  The 
evidence  was  that  there  was  not  much  smallpox  in  the 
neighborhood,  and  also  that  contact  infection  from  the  hos- 
pital could  not  be  excluded. 

In  New  Orleans'  a  large  number  of  cases  of  smallpox  were 
in  1900  treated  in  a  hospital  in  close  proximity  to  a  dense 
population,  but  without  evidence  of  extension.  Dr.  Theard 
writes  me  that  his  observations,  extending  over  nine  years 
since  that  time,  have  only  strengthened  his  views  then  ex- 
pressed, namely,  that  smallpox  virus  is  not  carried  from  hos- 

1  Niven,  Tr.  Epidemiol.  Soc,  Lond.,  1905,  n.  s.,  XXIV,  157. 

2  Rep.  Bu.  of  Health,  Phila.,  1903,  29. 

»  Rep.  Bd.  Health  of  the  City  of  New  Orleans,  1900-01,  33. 


INFECTION  BY  AIR  219 

pitals  by  the  air.  In  Brooklyn  smallpox  is  cared  for  at  the 
contagious-disease  hospital,  in  pavilions  about  twenty  feet 
from  those  occupied  by  measles  and  scarlet-fever  patients. 
There  has  been  no  extension  of  the  disease,  though  this  may 
be  largely  due  to  the  effort  to  keep  the  other  patients  well 
protected  by  vaccination.  But  there  is  also  a  considerable 
population  within  a  mile  of  the  hospital  which  has  never  been 
injuriously  affected  by  it.  In  Providence  the  smallpox  hos- 
pital is  distant  only  four  hundred  or  five  hundred  feet  from  a 
number  of  cottages  and  an  excursion  ground  frequented  by 
hundreds  of  persons  daily.  It  is  true  that  only  about  a  dozen 
patients  have  ever  been  there  at  one  time,  but  it  is  hard  to 
understand  wh}^  ten  patients  should  not  be  more  dangerous 
at  five  hundred  feet  than  one  hundred  patients  a  mile  dis- 
tant. In  Detroit  there  has  been  no  aerial  extension  of  the 
disease  from  the  hospital,  though  Dr.  Kiefer  writes  me  that 
there  is  a  considerable  populated  area  extending  to  within 
about  six  hundred  feet  of  the  buildings. 

Theoretical  Objections.  —  I  have  been  led  to  question 
this  theory  of  the  aerial  transmission  of  smallpox  for  various 
reasons.  From  what  is  known  of  the  nature  of  the  virus  of 
so  many  other  diseases  it  seems  highly  improbable  that  they 
are  carried  any  great  distance  by  the  air,  and  in  fact  it  is 
only  for  smallpox  that  this  mode  of  transmission  is  claimed. 
But  smallpox  virus  is  certainly  solid  matter,  and  it  certainly 
after  a  time  loses  its  vitality,  and  in  all  respects  other  than 
the  one  under  consideration  it  behaves  not  unlike  the  mate- 
ries  morhi  that  we  are  better  acquainted  with.  Again,  it 
would  be  most  remarkable,  if  the  disease  extends  from,  say, 
one  hundred  cases  to  the  distance  of  a  mile  with  sufficient 
intensity  to  infect  many  persons,  that  it  should  not  extend 
one  hundred  feet  from  ten  cases  or  even  from  one  case.  Why 
should  we  not  expect  aerial  infection  frequently  to  operate 
at  short  distances  from  single  cases?  Yet  such  transmission 
does  not  occur  unless  it  be  with  great  rarit}'.  How  rare  it  is 
for  any  claim  to  be  made  that  this  disease  has  been  carried 


220         THE  SOURCES  AND  MODES  OF  INFECTION 

across  the  street  from  house  to  house,  and  how  unique  a  rigid 
demonstration  of  such  an  occurrence  would  be!  How  often 
a  single  case  in  a  crowded  lodging  house,  ship's  steerage,  or 
hospital  ward,  fails  to  infect  others!  Yet  we  are  asked  to 
believe  that  one  hundred  cases  can  give  rise  to  a  whole  circle 
of  cases  a  half  mile  away.  Either  the  amount  of  virus  must 
depend  upon  the  number  of  patients,  or  it  must  under  hospi- 
tal conditions  develop  in  some  marvelous  way  outside  of 
the  body. 

Contradictions  in  Claims.  —  If  the  evidence  adduced  in 
favor  of  this  theory  is  examined,  several  suspicious  circum- 
stances are  noticed.  It  is  very  curious  that  a  material  sub- 
stance should  be  borne  by  the  air  without  reference  to  air 
currents ;  yet  in  the  earlier  reports  by  Powers  all  evidence  of 
such  currents  was  lacking.  It  is  true  that  in  later  reports 
the  wind  has  been  claimed  as  a  factor,  as  at  Gateshead  and 
Felling,  but  the  evidence  in  this  case  has  been  made  valueless 
by  more  detailed  search  for  the  origin  of  the  cases.  At  Liver- 
pool the  disease  was  distributed  in  different  directions  around 
the  three  hospitals,  so  that  if  air-borne  it  must  have  been 
independent  of  air  currents.  Savill  at  Warrington  even 
claimed  that  the  virus  diffused  against  the  wind.  The  reports 
of  the  Fulham  Hospital  give  one  .the  impression  that  the 
virus  of  smallpox  must  diffuse  like  a  gas,  which  certainly  is  not 
thinkable.  If  air-borne  at  all,  it  must  be  carried  as  is  dust  or 
as  are  liquid  particles.  If  the  virus  does  diffuse  in  all  direc- 
tions like  a  gas,  the  intensity  of  the  infection  should  diminish 
according  to  the  square  of  the  distance,  which  it  did  not  do 
at  Fulham  and  Liverpool.  Whether  it  diffuses  or  is  carried 
like  solid  particles,  the  houses  nearest  the  hospital  should  be 
by  far  the  most  intensely  infected.  Solid  particles  are  speed- 
ily, under  ordinary  conditions,  precipitated  to  the  ground,  as 
one  may  easily  note  by  observing  a  cloud  of  dust  of  any  kind. 
The  particles  of  smallpox  virus  ought,  then,  to  work  their 
chief  havoc  close  to  the  hospital.  Yet  this  incidence  was  not 
always  the  case,  even  at  Fulham,  and  similar  absence  of  near-by 


INFECTION  BY  AIR  221 

infection  was  noted  at  StockwelP  and  Liverpool.^  Again, 
quite  a  number  of  instances  are  given  where  large  institu- 
tions, like  schools,  workhouses  and  general  hospitals,  have 
been  located  within  the  area  alleged  to  have  been  severely 
infected  from  the  hospital,  and  yet  have  nearly  or  entirely 
escaped.  It  is  curious,  too,  that  in  the  only  instance  I  have 
noticed  in  which  the  sex  of  the  patients  in  the  infected  area 
was  given,  namely  Fulham,^  twenty-four  were  male  and 
seventeen  female.  As  so  many  more  men  are  away  from  their 
homes  at  work,  a  much  larger  female  population  must  be 
exposed  to  the  hospital  influence,  and  the  female  patients 
ought  to  be  more  numerous  than  the  male.  In  most  out- 
breaks of  smallpox  the  male  patients  are  more  numerous, 
because  the  men  move  about  more,  and  are  thus  more  likely 
to  be  exposed  to  cases  of  disease.  Again,  it  is  remarkable 
that  extension  should  be  more  likely  to  take  place  from 
acute  than  from  chronic  cases.  In  the  former  it  is  probable 
that  the  moist  mucous  membrane  is  the  only  source  of  infec- 
tion, while  in  the  latter  the  dried  crusts  are  known  to  be 
infectious. 

Distribution  of  Cases  Opposed  to  Theory.  —  It  is  thus  seen 
that  there  are  a  number  of  facts  and  a  number  of  theoretical 
considerations  opposed  to  the  theory  of  aerial  transmis- 
sion. That  smallpox  is  distributed  with  decreasing  inten- 
sity around  smallpox  hosjiitals  is  not  a  demonstration  that 
the  hospital  is  the  cause,  for  as  even  the  advocates  of  the 
theory  admit,  such  circles  of  infection  can  be  drawn  around 
other  points  in  a  city  during  epidemic  times,  as  was  indeed 
shown  by  Hope  in  Liverpool  in  1902-03  and  Clayton  at  Gates- 
head in  1903-04.  In  fact  most  outbreaks,  not  only  of  small- 
pox but  also  of  scarlet  fever  and  diphtheria,  are  in  a  general  way 
arranged  around  a  center,  with  more  cases  toward  the  center 

■  Rep.  Roy.  Com.,  Smallpox  and  Fever  Hospitals,  Ixjnd.,  1882,  92. 
*  Hope,  Observations  by  the  Med.  Off.  Health  on  the  Report  of 
Dr.  Reere  on  Smallpox  at  Liverpool.     C.  Tinling  &  Co.,  1905,  11. 
»  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  Lond.,  1880-81,  X,  Supl. 


222         THE  SOURCES  AND  MODES  OF  INFECTION 

and  fewer  toward  the  periphery.  It  is  not  remarkable  that 
occasionally  a  smallpox  hospital  is  found  near  the  center  of 
such  a  localization  of  disease.  As  favoring  this  chance,  it  must 
be  remembered  that  the  population  near  a  smallpox  hospital 
is  likely  to  be  of  the  poorer  classes,  upon  whom  the  weight  of 
this  disease  most  often  falls.  That  surrounding  outbreaks 
occur  chiefly  after  the  hospital  has  been  occupied,  is  only  to 
be  expected,  as  the  hospital  is  occupied  by  a  number  of  cases 
only  in  epidemic  times.  Much  stronger  evidence  would  be 
offered  by  the  advocates  of  this  theory  if  they  could  show 
that  no  other  explanation  of  the  origin  of  the  cases  could  be 
found  than  hospital  infection.  This  they  are  not  able  to  do, 
and  in  the  absence  of  such  evidence,  and  in  the  face  of  the 
evidence  against  the  theory,  the  theory  must  be  considered 
not  demonstrated. 

Cases  often  traced  to  Other  Sources.  —  A  good  deal  of 
evidence  in  regard  to  the  influence  of  hospitals  in  the  spread 
of  smallpox  was  collected  in  England  at  a  time  when  there 
was  no  registration  of  the  disease,  when  the  frequency  and 
importance  of  mild  cases  were  not  recognized  as  at  present, 
and  when  its  administrative  control  was  not  so  complete. 
Thus  it  was  stated  that  many  cases  of  smallpox  walked  to 
the  Homerton  Hospital  to  apply  for  admission,  ambulance 
drivers  stopped  at  public  houses,  children  of  the  neigh- 
borhood rode  on  the  steps  of  the  ambulance  and  the  patient's 
friends  inside.  It  would  not  be  surprising  if,  under  such  con- 
ditions, smallpox  spread  by  contact — and  indeed  it  was  admit- 
ted that  this  was  a  factor.  It  is  interesting  to  note  that  even 
Power  found  personal  exposure  the  cause  of  nine  out  of  thirty- 
two  cases  near  Fulham.  In  many  outbreaks,  where  there  is 
no  question  at  all  of  hospital  infection,  to  trace  the  source  of 
such  a  proportion  of  cases  is  all  that  can  be  expected.  Again, 
in  the  block  of  houses  nearest  the  same  Fulham  Hospital 
Dudfield  ^  showed  that  twenty  of  forty-one  cases  were  due  to 

^  Dudfield,  Rep.  Roy.  Com.,  Smallpox  and  Fever  Hospitals,  Lond., 
1882,  101. 


INFECTION  BY  AIR  223 

contact  infection.  According  to  Clayton,^  the  medical  officer 
of  health  of  Gateshead,  of  the  fifty-six  cases  of  smallpox 
within  one-half  mile  of  the  hospital,  on  which  Buchanan  bases 
his  conclusion  that  the  disease  was  carried  by  the  air,  fifty- 
two  were  traced  to  contact  infection.  Clayton  in  his  report 
on  this  outbreak  very  clearly  shows  the  fallacy  of  most  of 
the  arguments  presented  by  Buchanan.  In  Liverpool  it  was 
sho\vn  by  the  advocates  of  aerial  transmission  that  within 
one-quarter  of  a  mile  of  the  Parkhill  Hospital  the  rate  of 
incidence  of  smallpox  was  five  hundred  and  twenty-six  per  ten 
thousand  houses,  while  in  the  city  outside  of  hospital  areas 
it  was  only  eighty-five.  A  detailed  study  shows  that  this 
apparent  high  rate  depended  on  only  nine  patients  in  one 
hundred  and  seventy-one  houses,  and  Hope  shows  that  of  these 
nine,  four  were  knowm  to  be  due  to  direct  exposure  to  other 
cases.  A  careful  study  of  the  report  by  Reece^  of  this  Liver- 
pool outbreak  is  well  worth  while  by  all  interested  in  this 
subject.  A  most  ingenious  use  has  been  made  of  the  facts, 
but  an  impartial  critic  must  see  that  the  conclusions  arrived 
at  are  entirely  unwarranted.  If  one  is  still  in  doubt,  he  should 
read  the  report  of  Hope,^  the  medical  officer  of  health  of 
Liverpool,  which  clearly  and  briefly  refutes  all  the  arguments 
of  the  government  inspector. 

Conclusions  concerning  Smallpox.  —  It  appears  that  the 
evidence  for  the  aerial  transmission  of  smallpox  from  hospi- 
tals consists  solely  of  the  alleged  distribution  of  the  disease, 
at  a  gradually  decreasing  rate,  around  the  hospital,  the  exi.st- 
ence  of  the  cases  being  assumed  to  be  otherwise  unexplained. 
It  will  be  noted : 

1.  That  there  are  comparatively  few  instances  of  such  dis- 
tribution recorded. 

'  Clayton,  J.  Roy.  San.  Ins.,  1905,  XXVI,  199. 

'  Reeco,  Rep.  Loral  (Jov.  Bd.,  Lond.,  No.  208,  Smallpox  in  Liverpool, 
100.5. 

^  Hope,  Observations  by  the  Med.  Off.  Health  on  the  Report  o( 
Dr.  Reece  on  Smallpox  at  Liverpool.    C.  Tinling  &  Co.,  Liverpool,  1905. 


224         THE  SOURCES  AND  MODES  OF  INFECTION 

2.  That  many  instances  are  noted  where  there  was  no  such 
diffusion. 

3.  That  in  some  of  the  alleged  instances,  as  at  Fulham, 
Gateshead  and  Liverpool,  a  large  number  of  the  surrounding 
cases  have  been  shown  to  be  due  to  contact  infection. 

4.  That  in  the  long  run  the  amount  of  infection  around 
the  hospital  should  diminish  according  to  the  square  of  the 
distance.  This  it  does  not  do,  but  it  diminishes  irregularly, 
just  as  it  does  in  most  outbreaks  of  this  and  other  diseases 
due  to  contact  infection. 

5.  There  may  sometimes  be  contact  infection  from  the  hos- 
pital. The  surrounding  population  is  often  of  the  poorer  sort, 
and  is  consequently  particularly  subject  to  the  disease. 
Contact  infection  and  chance  may  be  sufficient  to  account 
for  those  instances  where  a  smallpox  hospital  is  the  center 
of  a  local  outbreak. 

The  evidence  in  favor  of  the  aerial  transmission  of  small- 
pox from  hospitals  is  so  slight  that  it  should  never  influence 
a  municipality  in  its  selection  of  a  hospital  site. 

The  success  of  Edinburgh,  New  York,  many  German  cities, 
and  the  Pasteur  Hospital  in  Paris,  in  caring  for  smallpox  in 
connection  with  other  diseases,  and  even  in  the  same  building 
with  other  patients,  indicates  that  the  theory  of  aerial  infec- 
tion has  little  basis  in  fact. 

Chicken  Pox.  —  Caiger,^  while  able  successfully  to  isolate 
scarlet  fever,  diphtheria  and  whooping  cough  in  his  hospital 
wards  by  the  cubicle  system,  had  several  transfers  of  chicken 
pox,  and  concludes  from  his  experience  that  this  disease  is 
frequently  air-borne. 

Scarlet  Fever  believed  to  be  Air-borne. — Scarlet  fever  also 
is  generally  believed  to  be  an  air-borne  disease.  One  reason 
for  this  is  doubtless  because  until  recently  the  desquamating 
epidermis  was  considered  to  be  the  chief  vehicle  of  infection. 
As  the  epidermis  comes  off  to  a  large  extent  as  very  fine  light 
particles,  it  was  but  natural  to  assume  that  these  would  be 
'  Rep.  Metropol.  Asylums  Bd.,  1907,  1908. 


INFECTION  BY  AIR  225 

readily  carried  by  the  air.  Recently  much  clinical  evidence 
has  accumulated  which  indicates  that  the  epidermal  scales 
are  not  infectious,  and  this  has  in  turn  developed  doubts  as 
to  the  disease  being  commonly  air-borne.  Whether  or  not 
the  epidermis  is  infectious,  there  seems  to  be  no  really  good 
evidence  that  the  disease  is  caused  by  air-borne  infection.  On 
the  contrary,  there  is  considerable  evidence  that  it  is  not  air- 
borne. 

Scarlet  Fever  in  Hospitals.  —  The  writer,  like  every  health 
officer,  has  frequently  noted  that  a  case  of  this  disease  may 
remain  in  school  or  hospital  ward  for  days,  or  sometimes  for 
weeks,  without  another  case  developing,  or  at  most  only  one 
or  two  cases.  Such  facts  indicate  that  the  disease  is  not 
easily  air-borne.  Visitors  to  fever  hospitals  do  not  contract 
scarlet  fever.  Thus,  of  three  hundred  to  four  hundred  non- 
immune students  who  visited  the  scarlet-fever  wards  of  the 
Philadelphia  hospital,  remaining  in  the  ward  from  twenty 
minutes  to  an  hour,  not  one  contracted  the  disease.'  Often- 
times scarlet  fever  does  attack  other  patients  in  hospitals, 
but  it  is  in  a  manner  to  indicate  contact  rather  than  air-borne 
infection.  When  contact  infection  is  rigidly  guarded  agai«ist, 
as  in  the  Pasteur  Hospital  in  Paris  and  in  many  English 
hospitals,  scarlet  fever  may  be,  and  is,  treated  in  the  same 
ward  with  other  diseases  without  cross  infection.  The  failure 
of  contagious  disease  to  spread  in  hospitals  when  contact 
infection  is  guarded  against  was  referred  to  in  some  detail 
in  the  chapter  on  contact  infection,  and  is  a  striking  demon- 
stration of  the  small  part  played  by  aerial  infection  in  the 
transmission  of  the  coininon  contagious  diseases. 

Scarlet  Fever  in  Dwellings.  —  I  have  been  much  impressed 
by  the  fact  that  scarlet  fever  and  likewise  diphtheria  do  not 
extend  from  one  family  to  another  in  the  same  house.  Most 
people  in  Providence  live  in  houses  of  two  or  three  stories, 
rarely  more,  with  one  or  two  families  on  each  floor.     Of  4306 

'  Welch  and  Schamberg,  Acute  Infectious  Diseases,  Phila.,  1905, 
346. 


226         THE  SOURCES  AND  MODES  OF  INFECTION 

"  other  families  "  living  in  the  same  house  with  scarlet-fever 
families,  only  6.8  per  cent  were  invaded.  Investigation  has 
shown  that  with  very  few  exceptions  the  infection  takes  place 
through  close  intercourse  before  the  disease  is  recognized  or, 
more  rarely,  after  the  isolation  has  been  terminated.  Most 
of  the  disease  in  the  "other  families  "  develops  within  a  few 
days  after  the  report  of  the  primary  case,  and  is  doubtless 
due  to  contact  infection  before  the  disease  is  recognized. 
Between  the  end  of  the  second  week  and  the  termination  of 
isolation,  the  disease  extends  to  other  families  in  the  house 
in  only  0.6  per  cent  of  the  cases,  and  in  most  of  these  it  is 
known  that  isolation  is  not  carried  out,  and  that  there  is  free 
intercourse  between  the  families.  If  the  disease  were  air- 
borne, it  would  certainly  pass  from  one  family  to  another  in 
the  house,  which  it  does  not  do. 

Scarlet  Fever  and  Outdoor  Air.  —  If  scarlet  fever  is  not 
air-borne  from  family  to  family  in  the  house,  one  would  not 
expect  it  to  be  borne  from  house  to  house  by  the  air.  Yet 
such  a  claim  is  sometimes  made,  and  even  that  the  virus  of 
the  disease  may  thus  be  transmitted  a  considerable  distance. 
A  number  of  the  reports  of  the  health  department  of  Phila- 
delphia contain  shaded  maps  purporting  to  show  an  excess 
of  this  disease,  as  well  as  of  smallpox,  in  those  parts  of  the 
city  near  the  hospital.  I  do  not  think  that  much  value  at- 
taches to  such  maps,  for  there  are  too  many  factors  involved, 
and  very  rarely  is  the  intensity  of  the  disease  as  great  close 
to  the  hospital  as  the  theory  demands.  Moreover,  around 
very  many  hospitals  no  such  distribution  of  the  disease  can 
be  shown.  Thus  Tarnissier,^  in  Paris,  found  that  the  En- 
fants  Malades  and  Trousseau  hospitals  could  not  be  con- 
sidered foci  of  infection.  The  same  is  true  of  the  scarlet-fever 
wards  in  Providence,  in  Detroit  and  in  Boston.  In  the  latter 
city,^  for  the  period  studied,  there  were  no  cases  of  the  disease 
within  one-eighth  of  a  mile  of  the  hospital,  while  in  the  next 

1  Tarnissier,  Semaine  med.,  1903,  267. 

2  Med.  and  Surg.  Rep.,  Bost.  City  Hosp.,  1897. 


INFECTION  BY  AIR  227 

eighth  of  a  mile  circle  there  were  sixty-eight  cases,  in  the  next 
seventy-one,  in  the  next  seventj^-five  and  in  the  next  seventy- 
two. 

Where  various  contagious  diseases  are  treated  in  different 
wards  of  the  same  hospital  there  is  sometimes  cross  infection. 
But  this  occurs  so  irregularl}^  as  to  time  and  place,  and  is  so 
limited  in  amount,  that  it  can  scarcely  be  attributed  to  any- 
thing but  contact  infection.  As  most  of  the  physicians  and 
nurses  in  our  contagious  hospitals  have  no  appreciation  of 
what  true  medical  asepsis  really  means,  it  is  surprising  that 
we  see  as  little  cross  infection  as  we  do.  If  scarlet  fever  does 
not  spread  within  the  walls  of  the  Pasteur  Hospital,  it  w^ould 
indeed  be  marvelous  if  it  should  extend  to  the  neighboring 
houses.  If  it  does  not  pass  from  family  to  family  in  the  same 
house,  it  would  be  most  surprising  if  it  could  be  wafted  by  the 
air  over  large  areas  around  the  Philadelphia  Hospital. 

Diphtheria  and  Sewer  Air.  —  Diphtheria  was  formerly  be- 
lieved to  be  a  filth  disease,  and  it  was  also  believed  that  air, 
especially  sewer  air,  was  frequently  the  vehicle  of  infection. 
Graham-Smith  refers  to  this,^  and  shows  th^t  there  is  no 
foundation  for  this  belief,  and  that  diphtheria  bacilli  have 
never  been  found  in  sewer  air.  He  says  that  Shattock  culti- 
vated bacilli  of  low  virulence  in  sewer  air  for  two  months,  but 
could  not  therebj'  increase  their  virulence.  As  I  was,  years 
ago,  prejudiced  in  favor  of  the  filth  origin  of  this  disease,  I 
gave  the  matter  careful  consideration  in  my  investigation  of 
cases,  but  was  never  able  to  find  any  evidence  that  sewer  gas 
was  an  etiological  factor.  Indeed  my  observation  of  diph- 
theria and  typhoid  fever  had  as  much  to  do  with  my  dis- 
carding the  filth  and  sewer-gas  theories  as  had  the  slowly 
accumulating  mass  of  bacteriological  evidence. 

Diphtheria  in  Hospitals  and  Dwellings.  —  From  an  epi- 
demiological standpoint  diphtheria  and  scarlet  fever  are  much 
alike.     As  the  latter  disease  has  been  supposed  to  be  air- 

^  Nuttall  iind  Clraham-Smith,  The  Bacteriology  of  Diphtheria, 
Cambridge,  1908,  321. 


228        THE  SOURCES  AND  MODES  OF  INFECTION 

borne  from  person  to  person,  so  has  the  former,  and  there  is 
the  same  lack  of  positive  evidence  for  both  diseases ;  and  the 
evidence  against  the  theory  is  much  the  same  for  diphtheria 
as  for  scarlet  fever.  As  is  stated  by  Graham-Smith,  bacterio- 
logical evidence  is  all  against  diphtheria  being  an  air-borne 
disease  except  in  rare  instances,  yet  probably  most  medical 
men  and  most  health  officers  consider  that  the  disease  is 
commonly  spread  in  this  way.  But  visiting  students  in  hos- 
pital wards  do  not  contract  it,  and  it  does  not  spread  when 
cases  of  this  disease  are  treated  in  pavilions  together  with 
other  diseases.  In  Providence  I  am  certain,  from  a  careful 
study  of  about  eleven  thousand  cases,  that  it  practically  never 
extends  from  one  family  to  another  in  a  house  except  by  per- 
sonal contact ;  and  it  does  not  extend  from  one  hospital  ward 
to  another  through  the  air.  At  North  Brother  Island  in  New 
York  there  is  a  diphtheria  ward  only  a  few  feet  from  a  tuber- 
culosis ward,  and  Dr.  S.  A.  Knopf  tells  me  that  there  is  no 
cross  infection.  Similar  conditions  are  noted  in  many  other 
hospitals.  Yet  Coutts^  recently  suggested,  without  any  evi- 
dence, that  certain  cases  of  diphtheria  were  due  to  street  dust, 
and  Cornell "  attempted  to  show  that  the  development  of  the 
disease  in  a  certain  locality  in  Philadelphia  was  due  to  air- 
borne infection.  At  best  there  was  in  the  instances  reported 
by  the  latter  only  a  possibility  of  aerial  infection,  with  the 
probabilities  very  much  against  it,  while  the  facts  as  stated 
did  point  very  strongly  to  the  existence  of  unrecognized  cases 
probably  spreading  the  disease  by  contact. 

Typhoid  Fever  and  Sewer  Air.  —  During  the  heyday  of 
the  sewer-gas  theory  of  disease,  numerous  outbreaks  of 
typhoid  fever  were  supposed  to  have  been  traced  to  infection 
by  means  of  air  from  sewers  and  drains.  A  number  of  typical 
reports  are  given  by  Roechling,^  and  others  may  be  found 
scattered  through  medical  literature.     In  none  of  these  is  real 

1  Coutts,  Pub.  Health,  Lond.,  1906-07,  XIX,  297. 

2  Cornell,  N.  York  M.  .J.  [etc.],  1905,  LXXXII,  1318. 

»  Roechling,  Sewer  Gas  and  Health,  Lond.  &  N.Y.,  1898,  30. 


INFECTION  BY  AIR  229 

proof  given  that  the  disease  was  thus  caused;  it  was  merely 
a  plausible  hypothesis.  Now  in  the  light  of  present-day 
knowledge  of  bacteria  and  sewer  air  it  is  no  longer  a  plausible 
hypothesis.  For  years  past  we  have  been  able  to  trace  most 
of  our  outbreaks  of  this  disease  to  water,  milk,  oysters  or 
other  food,  or  to  contact  infection.  In  most  instances  they 
could  not  be  due  to  sewer  air.  Usually  investigation  shows 
that  house  or  institution  outbreaks  cannot  possibly  be  due 
to  sewer  air,  and  where  such  an  hj'pothesis  is  permissible,  it 
usually  appears  highly  improbable.  I  see  almost  every  year 
small  house  outbreaks  of  typhoid  fever.  There  is  rarely  any 
evidence  of  the  escape  of  drain  air  into  the  house,  and  in 
almost  all  instances  such  escape  is  impossible.  Most  of  these 
house  outbreaks  indicate  contact  infection,  and  in  none  can 
contact  infection  be  excluded.  I  have  never  seen  the  slightest 
evidence  that  typhoid  fever  is  ever  due  to  sewer  air,  though  I 
began  my  public-health  work  with  a  fairly  strong  belief  in 
the  danger  from  this  source  and  sought  diligently  for  evi- 
dence of  it. 

Tjrphoid  Fever  and  Dust.  —  It  is  also  claimed  that  infected 
dust  ma}^  be  the  cause  of  outbreaks  of  this  disease.  This 
mode  of  infection  was  considered  to  be  of  some  moment  in 
the  Spanish- American  and  Boer^  wars,  and  certainly  bacterio- 
logical evidence  points  to  its  possibility.  Many  outbreaks  sup- 
posed to  be  due  to  dust  infection  have  been  reported.  Some 
of  these  are  referred  to  by  Germano^  and  Visbecq'  and  in  the 
Report  on  Typhoid  Fever  in  the  war  with  Spain,^  but  if  the 
original  reports  of  these  outbreaks  are  examined  it  will  be  seen 
that  the  evidence  is  very  weak  indeed.     Because  the  houses 

*  Tooth,  Brit.  M.  J.,  Lend.,  1900,  II,  1368;  Tr.  Clin.  See,  XXXIV, 
1213. 

^  Germano,  Ztsclir.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1897,  XXIV, 
403. 

'  Visbccq,  Arch,  de  med.  et  pharm.  milit.,  Par.,  1903,  XLI,  536. 

*  Ahst.  of  Rep.  on  the  Origin  and  Spread  of  Typhoid  Fever  in  U.  S. 
Military  Camps  during  the  Spanish  War  of  1898,  Wash.,  1900,  215. 


230       THE  SOURCES  AND  MODES  OF  INFECTION 

or  apartments  or  barracks  where  an  excess  of  typhoid  fever 
appears  are  situated  not  far  from  a  place  where  possibly 
infected  feces  are  deposited,  it  is  argued  that  the  disease  is 
caused  by  the  wind  blowing  over  the  spot  alleged  to  be  in- 
fected. Quill  ^  reports  that  typhoid  fever  was  brought  to  a 
certain  garrison  in  India  by  a  company  of  five  thousand  Boer 
prisoners,  many  of  whom  were  infected.  The  disease  con- 
tinued to  spread  among  the  prisoners  for  three  months,  until 
there  were  from  six  to  eight  hundred  cases.  Then  it  slowly 
appeared  among  the  garrison,  until  there  were  twenty-four 
cases.  It  was  supposed  to  be  caused  by  dust  blown  from  the 
latrines,  though  the  possibility  of  fly-borne  infection  is  men- 
tioned; but  an  extraneous  source,  or  unsuspected  contact 
infection,  is  highly  probable,  though  neither  is  excluded  or 
even  mentioned.  Mewius  ^  gives  an  ext^ellent  report  of  what 
he  considers  an  air-borne  outbreak,  but  it  appears  rather  to 
have  been  due  to  contact  infection,  a  typical  outbreak  of 
what  Winslow  calls  prosedemic  infection. 

The  fact  that  typhoid  fever,  dysentery  and  cholera^  can 
be  treated  in  a  well-managed  hospital  without  spreading  to 
other  patients  is  good  evidence  that  these  diseases  are  not 
air-borne  under  such  circumstances. 

Infantile  Diarrhea  and  Dust.  —  Newsholme,*  judging 
largely  from  the  fact  that  the  summer  diarrhea  of  infants 
occurs  with  greater  frequency  during  dry  seasons,  and  in 
towns  with  poor  scavenging,  infers  that  it  is  due,  to  some 
extent  at  least,  to  the  infection  of  milk  and  other  foods  by 
dust.  This  also  is  the  view  of  Hope,^  who  states  that  in 
Liverpool  in  six  Septembers  with  an  average  rainfall  of  13.8 
inches  there  were  373  deaths  from  diarrhea,  while  in  four- 

1  Quill,  Brit.  M.  .J.,  Lond.,  1902,  I,  383. 

"  Mewius,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1896,  XXIII, 
497. 

3  Woodruff,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  1160. 

*  Newsholme,  Pub.  Health,  Lond.,  1899-1900,  XII,  139. 

*  Hope,  Pub.  Health,  Lond.,  1898-99,  XI,  435. 


INFECTION  BY  AIR  231 

teen  Septembers  with  10.9  inches  of  rain  the  deaths  num- 
bered 573. 

Influenza.  —  During  the  present  pandemic  of  influenza, 
especially  at  its  commencement,  it  was  frequently  stated  that 
the  disease  was  chiefly  air-borne,  and  air-borne  to  great  dis- 
tances, even  across  the  Atlantic.  This  view  prevailed  be- 
cause the  disease  spread  with  such  great  rapidity,  appearing 
on  this  side  of  the  Atlantic  at  about  the  same  time  that  it 
did  in  England,  and  developing  almost  simultaneously  in  a 
large  number  of  localities.  The  subject  has  been  thoroughly 
studied  by  Leichtenstern,^  Parsons  ^  and  Schmid.  The  lat- 
ter's  observations  were  in  Switzerland  chiefly,  where  he  had 
ample  opportunity  to  study  the  outbreak  in  small  isolated 
communities.  His  work  is  reviewed  by  Leichtenstern,  who 
states  that  the  disease  never  developed  except  after  the  ad- 
vent of  some  stranger.  Parsons  studied  the  incidence  of  the 
disease  on  several  thousand  deep-sea  fishermen  and  on  four 
hundred  offshore  lighthouse  keepers,  and  in  no  instance  did 
the  disease  develop  except  as  the  result  of  contact  with  the 
sick  or  within  two  or  three  days  after  leaving  shore.  He 
says  there  is  no  evidence  whatever  that  the  disease  is  air- 
borne. Leichtenstern  studied  the  extension  of  the  disease  to 
distant  countries,  and  found  that  all  the  evidence  pointed  to 
personal  contact  as  the  only  factor  in  its  spread.  Thus  care- 
ful epidemiological  investigation  is  entirely  in  accord  with 
the  findings  of  bacteriology,  for  the  weak  resistance  of  the 
bacillus  makes  it  difficult  to  understand  how  the  disease  can 
be  carried  by  the  air  as  readily  as  is  often  alleged.  This 
feebleness  of  the  germ  renders  it  unlikely  that  influenza  is 
a  dust-borne  disease.  Of  course  it  may  spread  by  droplet 
infection,  but  the  increased  volume  of  the  secretions,  the  per- 
sistence of  the  bacillus  after  recovery  and  the  great  number 
of  carriers  give  such  opportunities  for  contact  infection  that 

*  Leichtenstern,  Nothnagel's  Encycl.  Pract.  Med.,  Influenza,  Phila. 
and  Ix)nd.,  1905,  .523. 

^  Parsons,  Brit.  M.  J.,  Lond.,  1891,  II,  303. 


232       THE  SOURCES  AND  MODES  OF  INFECTION 

it  is  hardly  necessary  to  attribute  much  importance  to 
aerial  infection,  as  the  term  is  generally  used,  or  to  fomites 
infection. 

Poliomyelitis.  —  Hill,^  from  a  careful  study  of  this  disease 
in  Minnesota,  was  led  to  suggest  the  theory  that  this  might 
be  a  dust-borne  disease.  He  finds  that  usually  outbreaks  occur 
in  hot,  dry  weather,  and  many  cases  had  long  exposure  to  dust 
infected  with  animal  feces,  especially  those  of  the  horse. 

Measles.  —  Measles  is  considered  a  typical  air-borne  dis- 
ease, at  least  within  doors,  but  the  experience  of  the  Pa- 
risian hospitals  shows  that  the  danger  of  infection  within 
wards  decreases  as  the  opportunity  for  contact  infection  is 
lessened." 

Infection  by  Air  at  Short  Range.  —  Most  of  the  discussion 
thus  far  has  related  in  large  part  to  alleged  extension  of 
disease  through  the  air  from  apartment  to  apartment,  or  from 
house  to  house,  or  from  hospital  to  adjoining  districts.  Trans- 
mission over  such  considerable  distances  might  be  rare  or 
even  impossible,  and  yet  nevertheless  the  air  might  be  the 
chief  vehicle  in  ordinary  institution  or  family  infection.  That 
it  is  believed  to  be  so  is  indicated  by  the  common  regulation 
that  a  wet  sheet  shall  be  hung  before  the  door  of  the  sick- 
room to  prevent  the  escape  of  germs,  by  the  wearing  of  caps 
by  visitors  and  the  disinfection  of  inaccessible  portions  of  the 
room.  If  we  ask  the  reason  for  this  universal  belief  in  the 
importance  of  air-borne  infection,  we  shall  find  that  it  is  based 
entirely  on  theory,  and  that  there  is  no  clinical  evidence 
at  all  to  indicate  that  such  a  mode  of  infection  is  of  any 
great  importance.  What  evidence  we  have  indicates  rather 
that  infection  by  means  of  the  air  is  of  comparatively  little 
importance. 

1  Hill,  Northwestern  Lancet,  Sept.  1,  1909  [reprint]. 

2  Grancher,  Cong.  Internat.  de  med.,  1900,  XIII,  C.-r.,  Par.,  Sect, 
de  med.  de  I'enfance,  478.  Moizard,  Bull,  et  mem.  Soc.  med.  d.  hop. 
de  Par.,  1900,  3  s.,  XVII,  683.  Martin,  Rev.  d'hyg.,  Par.,  1903,  XXV, 
256;  Bull,  et  mem  Soc.  med.  d.  hop.  de  Par.,  1904,  3  s.,  XXI,  297. 


INFECTION  BY  AIR  233 

Reasons  for  Belief.  —  The  real  reasons  why  people  gener- 
ally attach  so  much  importance  to  this  mode  of  infection  are, 
first,  the  hearty  belief  in  the  general  theory  of  aerial  infection 
which  has  prevailed  from  remote  antiquit}^,  and,  secondly, 
because  infection  so  often  takes  place  when  there  has  not  been 
any  kno\\Ti  contact.  Contact  is  the  most  certain  and  obvious 
mode  of  infection,  and  other  modes  should  not  be  assumed 
without  good  reason.  The  burden  of  proof  rests  on  those 
who  make  the  assumption. 

Air  and  Aseptic  Surgery.  —  The  history  of  aseptic  surgery 
is  very  suggestive  in  connection  with  the  theory  of  air-borne 
infection.  Lister  at  first  unquestionably  considered  the  air 
to  be  the  chief  source  of  wound  infection,  and  this  view  for 
awhile  dominated  surgical  practice.  Then  gradually  more 
and  more  attention  was  given  to  contact  infection,  contact 
with  instruments,  contact  with  the  patient's  own  skin,  con- 
tact with  the  operator's  hands.  As  danger  from  these  sources 
was  more  and  more  perfectly  guarded  against,  surgery  became 
more  and  more  successful  and  aerial  infection  was  less  and 
less  dreaded.  A  successful  surgeon  of  my  acquaintance  tells 
me  that  he  can  operate  with  as  little  wound  infection  in  a 
tenement  house  as  in  the  best  operating  room.  Ochsner^ 
says,  "Air  infection  is  not  impossible, but  practically  no  wound 
infection  is  to  be  considered  except  from  contact."  Most 
surgeons  at  the  present  time  consider  aerial  infection  of  very 
little  importance.  Nevertheless  it  has  been  shown,  as  we 
shall  see,  that  the  air,  even  of  well-constructed  operating 
rooms,  contains  considerable  numbers  of  living  pus-forming 
bacteria.  Yet  they  are  usually  not  numerous  enough  nor 
virulent  enough  to  infect,  and  unless  there  is  some  Other 
source  of  infection  the  wound  heals  aseptically.  Pus-forming 
bacteria  are  quite  resistant,  and  are  by  far  the  most  numerous 
and  ubiquitous  of  all  disease  germs  and  more  likely  to  be 
found  in  the  air,  and  the  fact  that  they  generally  fail  to  infect 
should  give  pause  to  any  claim  that  the  much  less  numer- 
*  Ochsner,  Clinical  Surgery,  Chicago,  1902,  26. 


234        THE  SOURCES  AND  MODES  OF  INFECTION 

ous  air-borne  germs  of  other  diseases  are  the  chief  source 
of  infection. 

Sewer  Air  and  Bacteria.  —  In  this  connection  the  relation 
of  sewer  air  to  the  transport  of  bacteria  should  be  referred  to. 
Winslow  ^  in  a  very  valuable  paper  gives  a  brief  history  of 
the  theories  on  this  subject,  and  shows  how  the  former  ideas 
as  to  the  great  danger  to  be  apprehended  from  sewer  air 
gradually  gave  way  before  increasing  knowledge  of  bacteria, 
and  particularly  after  it  was  determined  that  these  organisms 
are  not  readily  detached  from  moist  surfaces.  From  that 
time  it  was  generally  believed  that  sewer  air  had  little  or 
nothing  to  do  with  the  extension  of  the  infectious  diseases. 
The  subject,  however,  was  reopened  by  Andre wes  ^  and  Hor- 
rocks.^  The  latter  showed  that  under  natural  conditions 
B.  prodigiosus  and  also  the  bacillus  of  typhoid  fever  might 
be  carried  by  the  sewer  air  long  distances  and  escape  at  man- 
hole and  soil-pipe  openings.  Lewis  ^  also  showed  that  sewage 
bacteria  could  be  found  in  the  air  passing  over  a  sewage  farm, 
and  also  in  that  blowing  at  low  tide  over  a  beach  where 
sewage  was  discharged.  Winslow  by  a  series  of  careful  experi- 
ments confirmed  the  work  of  Horrocks,  but  went  further  and 
determined  the  number  of  bacteria  that  are  transported  in 
this  way.  He  found,  as  have  others,  that  mechanical  splash- 
ing may  produce  a  slight  local  infection  of  the  air  in  immediate 
contact  with  the  spray,  but  such  infection  extends  for  only 
a  very  short  distance  and  persists  for  not  more  than  a  minute 
or  two.  A  careful  quantitative  study  of  the  air  of  nineteen 
different  plumbing  systems  in  various  parts  of  Boston  showed 
that  very  few  sewage  bacteria  are  found  in  such  air.  These 
bacteria  were  found  only  four  times   in   200  liters  of  air, 

'  Winslow,  Rep.  to  San.  Com.  Nat.  Ass.  Master  Plumbers,  1907-09; 
Abst.  Am.  J.  Pub.  Hyg.,  Bost.,  1909,  V,  640. 

2  Andrewes,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1906-07,  XXXVI, 
183,  and  1907-08,  XXXVII,  266. 

3  Horrocks,  Pub.  Health,  Lond.,  1907,  XIX,  495. 
*  Lewis,  Scot.  M.  &  S.  J.,  Edin.,  1907,  XX,  487. 


INFECTION  BY  AIR  235 

and  then  in  the  presence  of  mechanical  spraying  of  sewage 
at  the  point  of  collection.  To  illustrate  the  paucity  of  dan- 
gerous bacteria  in  sewer  air  he  says: 

"  In  a  surface  water  of  good  quality,  like  that  of  New 
York  City,  the  colon  bacillus  can  almost  invariably  be  iso- 
lated from  ten  cubic  centimeters.  This  means  a  slight  degree 
of  intestinal  pollution,  but  experience  has  shown  that  the 
chance  of  infection  from  such  a  water  is  but  slight;  and  we 
drink  it  without  serious  alarm.  If  one  were  to  breathe  for 
24  hours  the  undiluted  air  of  a  house-drainage  system,  at 
any  point  not  immediately  infected  by  mechanical  splashing, 
it  appears  that  less  than  fifty  intestinal  bacteria  would  be 
taken  in;  for  the  daily  consumption  of  air  is  about  10,000 
liters,  and  in  200  liters  I  obtained  negative  results  from  air 
of  this  sort.  In  drinking  New  York  water  twice  as  many 
colon  bacilli  are  ingested  every  day,  for  1000  cubic  centi- 
meters is  a  small  amount  for  daily  consumption.  So  there 
would  be  less  danger  of  contracting  disease  from  continually 
breathing  the  air  of  a  vent  pipe,  or  of  a  soil  pipe,  except 
where  liquid  is  actually  splashing,  than  from  drinking  New 
York  water." 

Anthrax. —  Some  time  since,  while  considering  this  subject, 
it  occurred  to  me  that  anthrax  ought  to  be  air-borne  more 
often  than  any  other  disease.  The  spores  arc  extremely  resist- 
ant, and  are  found  in  great  numbers  in  hair,  wool,  etc.,  and 
the  manipulation  of  these  materials  is  quite  likely  to  raise  a 
considerable  amount  of  dust.  If  this  be  so,  and  if  floating 
germs  are  carried  to  the  alveoli  of  the  lungs,  as  is  alleged,  the 
pulmonary  type  of  this  disease  ought  to  be  very  common. 
Formerly  this  seems  to  have  been  the  case.  According  to  the 
report  of  the  Local  Government  Board,*  of  thirty-two  cases 
occurring  in  the  woolen  industry  of  Bradford  during  nine 
months,  twenty-three  were  of  the  internal  type.  Since  then 
great  effort  lias  been  made  to  eliminate  dust  as  much  as 
possible  from  the  woolen  and  other  industries  in  which  dry 
1  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1882-83,  XII,  98 


236         THE  SOURCES  AND  MODES  OF  INFECTION 

infected  material  is  handled.  As  a  consequence,  as  stated  in 
the  last  report  of  the  factory  inspector  which  I  have  at  hand/ 
of  four  hundred  forty-four  cases  of  industrial  anthrax  in  Eng- 
land from  1899  to  1907  only  twenty-one  were  of  the  pul- 
monary type,  and  all  of  these  twenty-one  were  in  the  dusty 
woolen  industry.  The  disease  is  not  nearly  so  common  in 
the  United  States,  owing  to  the  fact  that  less  infected  material 
is  imported,  but  of  fifteen  cases  in  Philadelphia  two  only  were 
internal.  Even  now,  under  the  best  conditions,  there  must 
be  considerable  infected  dust  caused  by  opening  and  separat- 
ing the  bales,  and  the  comparative  rarity  of  the  pulmonary 
type  of  the  disease  indicates  that  it  is  not  very  easily  air- 
borne, though  it  appears  almost  certain  that  some  cases 
develop  in  this  manner.  Furthermore,  it  appears  that  this 
disease  may  be  transmitted  by  the  air  even  out  of  doors. 
Legge  states  that  he  has  seen  two  horses  infected  by  feeding 
where  the  dust  from  the  blower  of  a  wool-sorting  room  was 
discharged,  and  Silberschmidt  ^  reported  a  similar  infection  of 
eight  out  of  twenty-two  horses  near  a  hair  factory  at  Zurich. 
Slight  Evidence  that  Disease  is  Air-borne.  —  It  is  thus 
seen  that  clinical  and  epidemiological  evidence  of  the  spread 
of  contagious  diseases  through  the  medium  of  the  air  is 
scanty.  No  proof  of  extension  through  the  external  air  is 
presented  for  any  important  disease  except  smallpox,  and 
this  is  far  from  conclusive.  I  have  never  seen  any  good  clin- 
ical evidence  that  diseases  are  air-borne,  even  indoors.  On 
the  contrary,  there  is  much  evidence  that  this  mode  of  infec- 
tion is  not  a  common  one.  The  reasons  for  the  widespread 
belief  in  the  transmission  of  disease  through  the  air  seem  to 
be  entirely  theoretical,  and  to  have  been  developed  simply 
because  no  other  satisfactory  explanation  was  at  hand.  Let 
us  now  consider  laboratory  and  experimental  evidence. 

1  Report   Chief  Inspector  of   Factories  and  Workshops,   1904,  49; 
1905,  49;  1906,  38;  1907,  56;  also  Legge,  Lancet,  Lond.,  1905,  I,  841. 

2  Silberschmidt,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1896, 
XXI,  455. 


INFECTION  BY  AIR  237 

Bacteria  not  given  off  from  Moist  Surfaces.  —  Among 
the  many  new  conceptions  which  resulted  from  the  study  of 
bacteriology,  one  of  the  most  novel  was  that,  contrary  to  all 
previous  ideas,  bacteria  are  not  given  off  from  and  are  not 
readily  detached  from  moist  surfaces  or  liquids  in  a  state  of 
rest.  This  was  first  shoAMi  by  Xageli^  and  has  been  amply 
confirmed  by  Buchner,"  Wernich,^  Huhs^  and  others. 

WTien  this  became  known,  numerous  experiments  were 
undertaken  to  determine  whether  the  expired  air  was  free 
from  germs,  as  in  accordance  with  the  newly  discovered  facts 
it  should  be.  Tyndall  was  the  first  to  show  that  bacteria 
are  not  found  in  expired  air,  and  Gotschlich  ^  cites  a  dozen 
or  so  workers,  all  of  whom  obtained  only  negative  results 
from  an  examination  of  the  expired  air.  According  to  Fliigge,^ 
Cadeac  and  Malet,  Grancher  and  Gennes,  and  ]\Iuller  were 
unable  to  find  tubercle  bacilli  in  the  ordinary  expiration  of 
phthisical  patients,  and  these  early  observations  have  been 
amply  confirmed  by  others. 

It  has  been  shown  not  only  that  air  currents  are  incapable 
of  removing  bacteria  from  liquids  but  also  that  such  currents 
do  not  remove  them  from  the  surfaces  of  solids.  Most  mate- 
rials which  contain  pathogenic  bacteria,  such  as  culture  media, 
saliva,  mucus,  pus,  excreta,  etc.,  present,  when  dry,  a  some- 
what hard  and  often  glazed  surface,  so  that  it  is  not  sur- 
prising that  exceedingly  strong  air  currents,  even  of  sixty 
meters  per  second,  do  not  remove  the  contained  germs.     This, 

'  Xiigeli,  Die  niederon  Pilzc,  Miinchen,  1877,  107,  Untersuchugen  in 
die  niederon  Pilze,  18S2. 

^  Njigeli  u.  Buchner,  Sitzungsbcr.  d.  Bay.  Akud.  d.  Wiss.,  Miinchen, 
7  June,  1879 . 

^  VVernich,  Virchow's  Arch.  f.  path.  Anat.  [etc.],  Bcrl.,  1880,  LXXIX, 
424. 

♦  Hubs,  Ztschr.  f.  Tuhork.  u.  Ileilstiittenw.,  Leipz.,  1906,  IX,  396. 

^  GotschHch,  Kollo  u.  Wa.ssermann,  Handbuch  (etc.),  Jena,  1902,  I, 
171. 

"  Fliigge,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
107. 


238         THE  SOURCES  AND  MODES  OF  INFECTION 

according  to  Gotschlich/  has  been  demonstrated  by  Nageli, 
Buchner,  Wernich,  Hamburger  and  Stern,  and  Fliigge.  Got- 
schlich  says  that  Honssell  found  it  impossible  to  detach 
bacteria  from  infected  clothing. 

Infection  in  Dust.  —  So  firmly  was  the  theory  of  aerial 
infection  intrenched  in  the  minds  of  men,  that  search  was 
made  for  some  other  means  than  the  expired  breath  by 
which  bacteria  might  get  into  the  air.  It  was  very  early 
found  that  many  bacteria  could  withstand  drying  for  con- 
siderable periods  of  time,  and  it  was  at  once  suggested  that 
material  containing  disease  germs  might  become  dry  and  pul- 
verized, and  that  the  resulting  infective  dust  might  readily 
be  transported  by  currents  of  air.  Indeed  Koch^  was  one 
of  the  earliest,  as  well  as  one  of  the  strongest,  supporters  of 
this  view. 

Resistance  of  Bacteria  to  Drying.  —  If  dust  is  a  vehicle 
for  the  transport  of  the  germs  of  disease,  and  bacteria  are 
air-borne  on  or  in  bits  of  dust,  or  float  as  separate  particles, 
they  must  withstand  a  considerable  amount  of  drying.  That 
some  species  do  retain  their  vitality  and  virulence  after 
becoming  quite  thoroughly  dry,  has  been  demonstrated.  Sys- 
tematic studies  of  the  effects  of  drying  and  of  light  on  dif- 
ferent disease-producing  bacteria  have  been  made,  and  almost 
every  germ  has  been  examined  from  this  standpoint  by  men 
particularly  interested  in  working  out  its  biological  characters. 
In  some  instances,  as,  for  example,  the  tubercle  bacillus,  the 
experiments  and  observations  are  very  numerous.  In  the 
chapter  on  fomites  infection,  the  resistance  of  the  different 
pathogenic  organisms  to  dryness  and  to  light  was  considered. 
While  some  species  were  shown  to  have  very  little  resisting 
power,  the  germs  surviving  for  a  few  hours  or  a  few  minutes 
only,  others,  like  the  bacilli  of  typhoid  fever,  diphtheria  and 

^  Gotschlich,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1902,  I, 
170. 

*  Koch,  Mit.  a.  d.  k.  Gesundheitsamte,  1884,  II,  Trans.  Sydenham 
Soc.  Pub.,  CXX. 


INFECTION  BY  AIR  239 

tuberculosis,  may,  when  dry,  retain  their  vitaUty  for  months. 
In  addition  to  the  general  knowledge  of  the  resisting  power  of 
bacteria,  which  has  been  accumulating,  special  and  systematic 
attempts  have  been  made  to  determine  directly  the  chances 
of  infection  by  air-borne  dust. 

Studies  on  the  Drying  of  Germs.  —  Among  the  earliest 
work  of  this  kind  was  that  by  Germano.^  He  employed  room 
dust  and  different  kinds  of  earth,  which  after  sterilization 
were  inoculated  with  cultures  of  bacteria  grown  in  various 
media.  He  found  that  generally  the  bacteria  perished  sooner 
in  room  dust  than  in  other  materials,  and  that  bacteria 
which,  like  the  typhoid  bacillus,  might  survive  for  months 
even  when  dried  on  clothing  or  solid  material,  would  speedily 
die  in  a  very  short  time  in  dust.  After  a  large  number  of 
experiments  he  concluded  that  cholera,  plague,  typhoid  fever, 
influenza  and  gonorrhea  could  not  be  dust-borne;  that  under 
certain  circumstances,  with  strong  air  currents,  streptococcus 
and  the  germs  of  pneumonia  and  of  diphtheria  might  be  air- 
borne, and  that,  besides  the  spores  of  anthrax  and  tetanus, 
many  of  the  pus  organisms,  meningococcus  and  the  tubercle 
bacillus,  might  be  transported  in  dust.  It  is  suspected  that 
he  did  not  employ  the  true  coccus  of  cerebro-spinal  meningi- 
tis, for  recent  workers  are  agreed  that  this  bacterium  has  very 
weak  powers  of  resistance.  His  results  with  the  pneumo- 
coccus  also  are  surprising,  as  this  too  is  rather  feeble. 

Neisser^  in  1898  made  a  careful  study  of  the  strength  of 
air  currents  necessary  to  move  dust  infected  with  various 
pathogenic  bacteria.  He  showed  that  currents  of  from  1 
to  4  mm.  per  second  are  sufficient  to  transport  room  dust, 
and  it  was  chiefly  with  such  currents  that  he  worked.  He 
used  from  twenty  to  thirty  drops  of  an  agar  culture  mixed 
with  30  c.c.  of  sterile  dust.  He  drew  dust  through  narrow 
tubes  in  a  rather  complicated  apparatus,  and  it  appears  that 

*  Germano,  Ztsolir.  f.  Hyg.  u.  Infertionskrankli.,  Lcipz.,  1897, 
XXIV,  403;  1897,  XXV,  4.39;  1S97,  XXVI,  60,  273. 

*  Neisser,  Ueber  Lauftstaub-Infection,  Inaug.  Uis.,  Breslau,  1898. 


240         THE  SOURCES  AND  MODES  OF  INFECTION 

the  conditions  were  too  far  removed  from  the  natural  to 
render  the  results  of  much  value.  Neisser's  conclusions  were 
that  diphtheria,  typhoid  fever,  plague,  cholera,  pneumonia, 
are  not  dust-borne  diseases,  but  that  spores,  most  of  the  pus 
organisms,  tubercle  bacilli,  and  the  germs  of  cerebro-spinal 
meningitis  may  be  so  carried.  It  will  be  seen  that  to  a  large 
extent  he  agrees  with  Germano,  but  it  is  to  be  noted,  however, 
that  his  tests,  like  those  of  Germano,  were  all  culture  tests, 
except  those  for  tuberculosis,  in  which  alone  animal  inocula- 
tions were  made.  Besides  such  systematic  work  as  that  of 
Germano  and  Neisser,  much  has  been  done  in  the  study  of 
special  diseases  by  men  particularly  interested  therein. 

Drying  of  Typhoid  Bacilli.  —  Firth  and  Horrocks  ^  found 
that  the  typhoid  bacillus  would  live  for  23  days  in  sand  dry 
enough  to  be  blown  by  the  wind.  Harrison  and  Harrison,^ 
working  in  India,  recovered  the  organism  after  118  hours 
when  kept  in  diffused  light  in  very  dry  dust.  Aldridge^ 
moistened  sand  with  urine  containing  typhoid  bacilli  on 
three  successive  days,  and  dried  it  on  the  fourth  day,  and 
blew  it  with  a  bellows  over  sterile  bouillon.  He  recovered 
the  bacillus  on  the  1st,  4th  and  9th  day  thereafter. 

Horrocks^  showed  that  the  micrococcus  of  Mediterranean 
fever  would  survive  in  dry  soil  for  about  3  weeks. 

Drying  of  Diphtheria  Bacilli.  —  Flugge  ^  says  that  diph- 
theria bacilli  perish  when  dry  enough  to  be  blown  about  in 
dust.  This  is  confirmed  by  Pernice  and  Scagliosi  and  Reyes." 
Reyes  found  they  would  live  for  14  days  in  dry  sand. 

Drying  of  Plague  Bacilli.  —  Tidswell,^  experimenting  with 
dust  of  various  kinds,  could  not  recover  the  bacillus  of  bu- 

1  Firth  and  Horrocks,  Brit.  M.  J.,  Lend.,  1902,  II,  936,  1094. 
^  Harrison  and  Harrison,  J.  Roy.  Army  Med.  Corps,  Lond.,  1904, 
II,  721. 

'  Aldridge,  Indian  M.  Gaz.,  Calcutta,  1903,  XXXVIII,  249. 

'  Horrocks,  J.  Roy.  Army  Med.  Corps,  Lond.,  1905,  V,  78. 

5  Flugge,  Ztschr.  f .  Hyg.  u.  Infectionskrankh.,  Leipz.,  1895,  XVII,  401. 

*  Cited  by  Germano. 

'  Tidswell,  Rep.  on  Plague  in  Queensland,  1902,  67, 


INFECTION  BY  AIR  241 

boiiic  plague  after  11  daj-s  when  the  dust  was  dried  under 
natural  conditions,  and  it  usually  died  within  3  or  4  days. 
When  dried  very  slowly  it  lived  about  twice  as  long.  Rose- 
nau^  found  that  this  bacillus  did  not  live  in  dried  bone  dust 
over  6  days,  and  he  did  not  recover  it  from  dry  and  sterile 
garden  soil  after  1  day. 

Drying  of  Tubercle  Bacilli.  —  More  attention  has  been 
given  to  the  tubercle  bacillus  than  to  any  other  pathogenic 
organism.  Besides  other  experiments  referred  to  elsewhere 
in  these  pages  it  may  be  mentioned  that  Kirstein^  experi- 
mented with  various  kinds  of  dust,  and  could  not  find  living 
tubercle  bacilli  after  8  days.  The  dust  was  artificially 
infected  and  exposed  to  diffused  light.  He  thinks  droplet  in- 
fection far  more  important  than  dust  infection.  Cadeac  ^ 
was  unable  to  reduce  sputum  to  dust  until  it  had  been  dried 
10  to  12  daj's,  while  the  tubercle  bacilli  had  nearly  died  out 
on  the  6th  day.  Even  when  pulverized  sputum  is  injected 
into  animals,  tuberculosis  rarely  develops,  and  it  must  be 
still  rarer  as  the  result  of  inhalation.  Sticher  ^  also  and 
Beninde  ^  found  it  difficult  to  demonstrate  living  bacilli 
in  dried  and  pulverized  sputum  under  natural  conditions. 
Nevertheless  most  observers  do  find  living  tubercle  bacilli  in 
dust,  though  usually  with  weakened  virulence. 

Drying  of  Cholera  Spirilla.  —  According  to  Germano,  chol- 
era spirilla  maj^  sometimes  survive  in  dust  for  3  days,  but 
oftentimes  they  die  in  1  day.  He  says  that  Honssell  was 
never  al)le  to  obtain  living  spirilla  from  infected  dust, 
though  Uffelmann  was  able  to  do  so   for  a  short  period. 

'  Rosenau,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.  Hyg.  Lab.  Bull. 
No.  4,  1901. 

*  Kirstein,  Ztschr.  f.  Hyg.  u.  Infoctionskrankh.,  Leipz.,  190.5,  L,  186. 
»  Cad6ac,  Lyon  M6d.,  1905,  CV,  893;  also  Lyon  Med.,  1908,  CXI, 

532. 

*  Sticher,  Zt>=(;hr.  f.  Hyg.  u.  Infoctionskrankh.,  Loipz.,  1899,  XXX, 
163. 

*  IJenindc,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
193. 


242    THE  SOURCES  AND  MODES  OF  INFECTION 

William^    believes    that    cholera    cannot    be    a   dust-borne 
disease. 

Tubercle  Bacilli  in  Dust.  —  Of  more  practical  importance 
than  experiments  with  artificially  infected  dust  is  the  deter- 
mination of  the  presence  or  absence  of  disease-producing 
bacteria  in  supposedly  infected  localities.  The  chief  interest 
in  such  investigations  has  centered  in  tuberculosis.  Cornet  ^ 
has  made  a  more  extensive  study  than  any  one  else  of  the 
natural  distribution  of  tubercle  bacilli  in  dust.  He  examined 
147  specimens  of  dust  collected  from  hospital  wards,  dis- 
pensaries, private  houses,  streets,  etc.  No  bacilli  were  found 
in  the  street  or  in  places  not  occupied  by  the  tuberculous, 
and  even  in  the  environment  of  the  consumptive  germs  were 
found  only  when  the  patient  was  careless  in  the  disposal  of 
sputum.  Cornet's  observations  have  been  confirmed  by  Rem- 
bold,  Kriiger,  Kastner,  Ballinger,  Kusterman,  Le  Noir  and 
Camus  and  Enderlin,  besides  others  elsewhere  referred  to. 
Gotschlich  ^  examined  one  hundred  and  nineteen  specimens 
of  dust  from  streets  and  public  places  and  was  not  able  to 
demonstrate  the  presence  of  tubercle  bacilli.  While  most 
observers  have  been  unable  to  find  the  tubercle  bacillus  in 
street  dust,  it  is  said  to  have  been  found  by  Manfredi ''  and 
Schnirer.^  Prausnitz  ^  and  Petri  ^  obtained  tubercle  bacilli 
from  the  dust  in  railway  carriages,  and  Bissell  ^  found  them 
in  tramcars  in  Buffalo. 

1  William,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1893,  XV,  166. 

^  Cornet,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1885,  V,  98; 
Nothnagel's  Encyclopedia  of  Pract.  Med.,  Phila.  &  Lond.,  1907,  Tuber- 
culosis, 85. 

»  Gotschlich,  Die  Verbreitung  der  Tuberkelbacillen  in  Staub  von 
Raumen  mit  starkem  Menschenverkehr,  Inaug.  Dis.,  Breslau,  1903. 

*  Manfredi,  Jahresb.  u.  d.  Fortschr.  .  .  .  d.  path.  Mik.,  Baumgarten, 
1891,  VII,  570. 

5  Schnirer,  Wien.  med.  Presse,  1891,  XXXII,  3. 

«  Prausnitz,  Arch.  f.  Hyg.,  Miinchen  u.  Leipz.,  1891,  XII,  192. 

'  Petri,  Arb.  a.  d.  k.  Gesund.-Amt.,  Berl.,  1894,  IX,  76. 

"  Bissell,  N.  York  M.  J.,  1895,  LXII,  783. 


INFECTION  BY  AIR  243 

Some  observers  have  not  found  the  bacilU  so  numerous  as 
did  Cornet.  Thus  Hill/  following  Cornet's  methods,  obtained 
virulent  bacilli  in  but  5  of  496  swabbings  from  private 
houses  where  there  were  cases  of  the  disease,  and  in  3  of 
180  swabbings  from  hospital  wards. 

Heymann '  has  criticised  Cornet's  findings  on  the  ground 
that  the  latter  recovered  the  dust  by  means  of  moist  swabs, 
thereby  perhaps  taking  up  many  bacilli  which  were  attached 
to  the  floor,  table,  etc.,  and  which  would  not  therefore  have 
any  part  in  air-borne  infection.  He  does  not  find  living 
bacilli  so  numerous  in  dust  as  did  Cornet.  Heymann  in  120 
tests  found  them  only  one-third  as  often,  but  Coats,^  follow- 
ing Heymann's  methods,  was  able  by  inoculation  tests  to 
demonstrate  the  presence  of  tubercle  bacilli  in  66  per  cent  of 
specimens  of  dust  obtained  from  fourteen  rooms  occupied  by 
tuberculous  patients.  On  the  whole,  it  appears  that  virulent 
tubercle  bacilli  are  quite  commonly  found  in  the  dust  of 
rooms  occupied  by  careless  tuberculous  patients. 

In  this  connection  may  be  mentioned  an  experiment  of 
Heymann's  in  which  he  rubbed  and  shook  a  sputum-infected 
handkerchief,  after  two  days'  drying,  in  a  closed  box,  and 
found  floating  bacilli  after  the  lapse  of  an  hour. 

Meningococcus  in  Dust.  —  Jaeger^  claimed  to  have  found 
the  meningococcus  on  the  floor  of  barracks,  and  Nettt^r^  the 
pneumococcus  in  the  dust  of  a  sick-room  four  weeks  after  the 
case  was  removed,  but  from  what  is  now  known  of  the  resist- 
ance of  these  bacteria  this  is  highly  improbable.  Wash- 
bourn  and  Eyre"  found  the  pneumococcus  in  dust  from  a 
ward  and  laboratory  at  Guy's  Hospital,  but  failed  to  find  it  in 

1  Hill,  Am.  Pul).  Health  Ass.  Rep.,  1902,  XXVIII,  209. 
^  Heymann,    Ztschr.    f.    Hyg.    u.    Infectionskrankh.,    Leipz.,    1901, 
XXXVIII,  21. 

'  Coats,  Trans.  Brit.  Cong,  on  Tuberculosis,  1901,  I,  p.  88. 

♦  Jaeger,  Deutsche  mcd.  Wchnschr.,  1899,  XXV,  472. 

*  Netter,  Compt.  rend.  Soc.  de  hiol.,  Par.,  1897,  IV,  538. 
"  Washbourn  and  Eyre,  Lancet,  Lond.,  1902,  II,  1440. 


244        THE  SOURCES  AND  MODES  OF  INFECTION 

street  dust.  Washbourn  says  that  it  has  also  been  found  in 
dust  by  Emmerich,  Maximowitch  and  Netter. 

Diphtheria  Bacilli  in  Dust.  —  These  bacilli  have  been  found 
in  the  dust  of  a  scarlet-fever  ward/  and  are  said  to  have  been 
found  in  a  diphtheria  ward  by  Richardiere  and  Tallemer,^ 
but  Schlichter  ^  could  not  find  them  in  a  hospital  in  Vienna. 
Cobbett  *  exposed  plates  in  a  diphtheria  ward,  but  could 
obtain  no  bacilli  except  when  the  plates  had  been  touched 
by  the  fingers  of  the  patients. 

Dust  and  Other  Diseases.  —  There  has  been  much  dis- 
cussion of  late  in  England  about  the  necessity  for  disinfecting 
schoolrooms,  and  examination  of  school  dust  has  shown  the 
presence  of  colon  bacilli  ^  and  the  pus  organisms.*' 

General  Conclusions.  —  While  these  facts  relating  to  the 
resistance  of  disease  germs  to  drying,  and  their  presence  in 
supposedly  infected  localities,  afford  no  definite  information 
as  to  the  danger  to  be  apprehended  from  infection  by  air- 
borne dust,  they  do  lead  to  some  tentative  conclusions.  It 
is  scarcely  possible  that  gonorrhea,  influenza,  cerebro-spinal 
meningitis  and  pneumonia  can  be  dust-borne.  It  is  possible, 
perhaps,  but  highly  improbable,  that  plague  and  cholera  can 
be  so  borne.  The  bacteriological  evidence  indicates  that  the 
germ  of  typhoid  fever,  dysentery,  Mediterranean  fever,  diph- 
theria, tuberculosis  and  suppuration  may  be  carried  by  float- 
ing dust,  and  it  is  certainly  possible  for  anthrax  and  other 
spores. 

Danger  from  Dust  Slight. — Bacteriology  also  teaches  what 
is  often  forgotten,  that  pathogenic  bacteria,  with  the  ex- 
ception of  spores,  die  off  quite  rapidly  when  dried,  and  that 
the  survivors  usually  have  a  weakened  virulence.     If  in  a 

1  Renney,  Pub.  Health,  Lond.,  1905,  XVII,  706. 

'  Richardiere  et  Talleraer,  Gaz.  d.  mal.  enfant  [etc.],  Par.,  1899,  X. 

»  Schlichter,  Arch.  f.  Kinderh.,  Stuttg.,  1S92,  XIV,  129. 

*  Cobbett,  J.  Royal  San.  Inst.,  Lend.,  1904,  XXV,  405. 

*  Hewlett,  Lancet,  Lond.,  1909,  I,  741,  815,  889. 
«  Kerr,  Med.  Off.  Educa.,  Lend.,  1908,  31. 


INFECTION  BY  AIR  245 

sick-room  or  hospital  ward  the  germs  of  disease  are  scattered 
so  freely  on  the  floor  or  room  contents  that  enough  of  them 
can  survive  drying  and  pulverization  to  float  in  the  air  and 
cause  disease,  the  opportunities  for  contact  infection  with  the 
comparatively  fresh  infective  material  must  be  very  great,  so 
great,  it  seems  to  me,  that  infection  by  air  under  such  condi- 
tions must  be  very  insignificant  or  entirely  negligible  as  com- 
pared with  infection  by  contact. 

Droplet  Infection.  —  Another  way  in  which  living  bacteria 
may  be  carried  by  the  air  is  in  tiny  floating  particles  of  liquid. 
Fliigge^  was  the  first  to  call  attention  to  the  fact  that  during 
speaking,  and  especially  during  loud  talking,  coughing  and 
sneezing,  tiny  droplets  of  saliva  are  thrown  off  from  the 
mouth.  Indeed  such  droplets  may  be  readily  seen  in  the 
proper  light,  and  it  hardly  needed  special  experiment  to  prove 
their  existence.  Nevertheless,  Fliigge^  and  Laschtschenko,^ 
by  infecting  the  mouth  with  B.  prodigiosus,  showed  that 
germ-carrying  droplets  are,  during  coughing,  borne  to  a  dis- 
tance of  nine  meters  in  front  of  the  mouth.  These  droplet 
experiments  have  been  repeated  with  confirmatory  results  by 
Goldie,  Esmarch,  B.  Frankel,  Moller,  Hiibner,  Weismayr  and 
Koniger,  and  the  last  mentioned  has  shown  that  the  droplets 
may  be  found  two  meters  behind  the  person  coughing.^ 
Goldie  showed  that  in  fourteen  per  cent  of  the  cases  tubercle 
bacilli  could  be  caught  on  plates  after  a  single  act  of  coughing. 
Every  patient  examined  at  one  time  or  another  gave  positive 
results.  No  bacilli  were  found,  even  as  near  as  six  inches, 
during  deep  breathing,  but  after  coughing  they  could  be 
recovered  from  all  parts  of  the  room. 

*  Fliigge,  Ztschr.  f.  Ilyg.  u.  Infectionskrankh.,  Leipz.,  1897,  XXV, 
179. 

*  Fliigge,  Ztsch.f.  Hyg.  u.  Infectionskrankh.,  Lcipz.,  1899,  XXX,  107. 
'  La.schtschenko,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899, 

XXX,  125. 

*  Koniger,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1900,  XXXIV, 
119. 


246         THE  SOURCES  AND  MODES  OF  INFECTION 

Amount  of  Droplet  Infection.  —  Since  it  has  been  shown  by 
Fliigge  that  droplets  from  speaking  may  float  for  from  five 
to  six  hours,  and  be  transported  by  air  currents  of  only  one 
mm.  per  second,  it  is  not  surprising  that  they  should  be  car- 
ried such  distances.  Nor  is  it  surprising  that  Hutchinson^ 
was  able  to  prove  that  a  fine  spray  of  a  culture  of  B.  pro- 
digiosus  was  carried  fifty-five  meters  along  a  corridor,  and  up 
two  flights  of  stairs,  and  also  a  considerable  distance  out  of 
doors.  Others  have  shown  that  the  bacteria  of  the  mouth 
may  be  carried  by  the  air  during  speaking  over  a  large  room 
or  hall.^  Leon^  showed  that  in  speaking  three  hundred 
words  250,000  bacteria  were  thrown  off  from  the  mouth,  and 
Ziesche^  found  over  20,000  tubercle  bacilli  on  a  plate  324 
sq.  cm.  exposed  for  half  an  hour.  But  it  has  further  been 
shown  by  Kirstein^  and  Koniger*^  and  Laschtschenko^  that 
the  size  of  the  droplets  and  the  distance  they  can  be  carried 
depend  to  a  large  extent  upon  whether  the  liquid  is  thin  and 
watery  or  a  thick  mucus.  Hence  we  should  expect  that 
droplets  of  thick  sputum  would  not  be  carried  nearly  so 
far  as  droplets  of  more  liquid  saliva,  and  according  to 
Goldie*  droplets  of  the  saliva  rarely  carry  bacilli  but  only  the 
droplets  of  sputum. 

Quantitative  Experiments. — Since  the  above  was  written 
Winslow  and  Robinson^  have  published  a  very  interesting 

1  Hutchinson,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1901, 
XXXVI,  223. 

2  Gordon,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1902-03,  XXXII, 


421. 

3 
4 
5 

123. 

6 

119. 

'  Laschtschenko,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899, 
XXX,  125. 

"  Goldie,  Canadian  Pract.  &  Rev.,  Toronto,  1899,  XXIV,  433. 

'  Winslow  and  Robinson,  Jour.  Infect.  Dis.,  Chicago,  1910,  VII.  17. 


Leon,  Arch.  f.  klin.  Chir.,  Berl.,  1903-04,  LXXII,  904. 

Ziesche,  Ztschr.  f .  Hyg.  u.  Infectionskrankh,  Leipz.,  1907,  XLVII,  50. 

Kirstein,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1900,  XXXV, 

Koniger,  Ztschr.  f .  Hyg.  u.  Infectionskrankh.,  Leipz.,  1900,  XXXIV, 


INFECTION  BY  AIR  247 

paper  on  this  subject  giving  an  excellent  resume  of  previous 
investigations.  They  repeat  the  experiments  of  some  of  the 
European  writers,  and  like  them  they  find  that  if  the  mouth 
of  a  speaker  is  infected  with  a  specific  germ,  as  B.  prodigiosus, 
agar  plates  exposed  in  different  parts  of  the  room  show  nu- 
merous colonies  of  the  bacillus.  They  also,  by  the  exposure 
of  plates  in  the  room  with  the  speaker,  recovered  Gordon's 
Streptococcus  salivarius,  which  is  a  normal  inhabitant  of  the 
mouth.  The  authors  emphasize  the  distinction  noted  by 
others  between  the  larger  droplets  of  mouth  spray  which  con- 
tain the  most  bacteria  and  which  settle  out  of  the  air  in  the 
space  of  a  few  feet  from  the  mouth  and  the  smaller  droplets 
which  float  for  a  longer  time  and  may  pass  to  some  distance 
from  the  speaker,  and  which  alone  may  be  considered  as  prop- 
erly constituting  an  infection  of  the  air.  The  chief  interest 
in  their  studies  attaches  to  their  quantitative  work  carried 
out  on  the  lines  devised  by  Winslow  for  his  investigations  of 
sewer  air.  Out  of  140  liters  of  air  taken  at  various  points  in 
the  room  immediately  after  10  to  50  minutes'  loud  speaking 
by  a  person  whose  mouth  was  infected  with  B.  prodigiosus, 
the  bacillus  was  found  seven  times.  Of  74  liters  examined  for 
Streptococcus  salivarius  none  were  found  to  contain  this  nor- 
mal inhabitant  of  the  mouth.  The  authors  consider  that  an 
artificial  infection  of  the  mouth  may  give  too  high  an  index 
of  air  contamination,  wliilc  the  normal  germs  of  the  mouth 
may  be  thrown  off  in  smaller  numbers  than  are  the  disease 
germs  from  sick  persons.  The  authors  conclude  that  these 
experiments  furnish  "no  basis  for  a  belief  that  tuberculosis 
or  any  other  disease  is  contracted  to  an  appreciable  extent 
through  the  inspired  air  "  and  are  "  in  harmony  with  the 
conviction  now  generally  gaining  ground  that  aerial  infection 
of  any  sort  is  a  minor  factor  in  the  spread  of  zymotic  disease." 
L-epra  Bacilli.  —  Schiiffer  '  was  able  to  recover  bacilli  from 
a  leprous  i)atient  by  holding  cover  glasses  a  short  distance  in 
front  of  the  face  while  the  patient  was  speaking  and  coughing. 
»  Schaffcr,  Arch.  f.  Dermat.  u.  Syph.,  Wicn,  1898,  XLIV,  159. 


248        THE  SOURCES  AND  MODES  OF  INFECTION 

Pneumococcus.  —  Wood  '  found  that  pneumococci  did  not 
retain  their  vitahty  in  floating  droplets  over  one  hour,  and 
not  half  an  hour  in  diffused  light. 

Influenza  Bacilli.  —  According  to  Gotschlich,'  droplets  con- 
taining influenza  bacilli  will  float  for  five  hours.  Very  little 
has  been  done  to  demonstrate  the  existence  of  infected  drop- 
lets in  any  other  diseases. 

Bacteria  found  in  Air.  —  Having  shown  that  bacteria  may 
float  in  the  air  on  particles  of  dust  and  in  droplets  of  liquid, 
we  must  next  inquire  whether  pathogenic  germs  have  actually 
been  found  in  the  air.  Graham-Smith^  examined  the  air  of 
the  House  of  Commons  for  pathogenic  bacteria  with  negative 
results,  as  did  Andrewes^  and  Gordon^  the  air  in  the  streets 
of  London.  Little  light  is  thrown  on  our  present  problem 
by  these  and  similar  negative  tests  of  outdoor  air  or  of  air 
away  from  the  vicinity  of  the  sick.  Far  more  interest  and 
value  attach  to  the  examination  of  air  in  the  vicinity  of 
cases  of  infectious  sickness. 

Tubercle  Bacilli  in  Air.  —  Heymann**  was  able  to  recover 
virulent  tubercle  bacilli  from  the  air  of  a  small  chamber  in 
which  was  placed  a  coughing  tuberculous  patient.  Similar 
results  were  obtained  by  Laschtschenko.^  Cprbett^  recovered 
acid-fast  bacilli  from  the  ventilating  shaft  of  a  hospital,  but 
made  no  inoculation  tests.  Klein  ^  infected  guinea  pigs  by 
exposure  in  the  vent  shaft  of  Brompton  Hospital.     According 

1  Wood,  J.  Exper.  M.,  N.  Y.,  1905,  VII,  592. 

^  Gotschlich,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1902, 1, 175. 

3  Graham-Smith,  J.  Hyg.,  Cambridge,  1903,  III,  498. 

^  Andrewes,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1906-07,  XXXVI, 
187. 

5  Gordon,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1902-03,  XXXII, 
421. 

^  Heymann,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1901, 
XXXVIII,  21. 

'  Laschtschenko,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899, 
XXX. 

"  Corbett,  St.  Paul  M.  J.,  St.  Paul,  Minn.,  1904,  VI,  735. 

'  Stevenson  and  Murphy,  Hygiene  and  Public  Health,  II,  212. 


INFECTION  BY  AIR  249 

to  Cornet  and  Meyer/  Williams,  Celli  and  Guamieri,  Wehde, 
and  Baumgarten  have  examined  air  for  tubercle  bacilli  with 
negative  results.  Recently  Le  Xoir  and  Camus^  demon- 
strated by  inoculation  tubercle  bacilli  in  the  dust  of  a  hospi- 
tal ward,  but  they  could  not  obtain  them  by  the  filtration 
of  even  53,000  liters  of  the  air.  Viewing  the  human  nose  as 
a  filter,  they  took  swabbings  from  the  nose  of  physicians  and 
attendants  of  phthisical  patients,  but  could  not  demonstrate 
tubercle  bacilli  by  inoculation,  though  they  found  them  in 
the  nose  of  the  patients  themselves.  Cornet  considers  that 
the  germs  are  so  sparsely  distributed  that  one  ought  not  to 
expect  to  obtain  them  by  the  filtration  of  even  1000  liters 
of  air.  He  says  that  the  finding  of  tubercle  bacilli  in  settled 
dust  has  as  much  bearing  on  air  infection  as  finding  it  in 
the  air  and  is  a  much  easier  operation.  It  does  not  appear 
that  Cornet  is  correct  in  his  contention  that  the  examination 
of  dust  is  of  more  practical  importance  than  the  examination 
of  air.  The  examination  of  dust  can  throw  no  light  on  the 
number  of  bacteria  floating  in  the  air  at  any  one  time,  and 
as  Winslow  in  his  work  on  sewer  air  previously  referred 
to  has  so  clearly  pointed  out,  a  quantitative  examination  of 
the  floating  bacteria  is  necessary  if  we  wish  to  determine  the 
real  danger  from  the  inhalation  of  the  air.  No  such  enumer- 
ation of  tubercle  bacilli  seems  to  have  been  made,  and  the 
difficulty  of  finding  them  suggests  that  they  are  not  very 
numerous,  even  in  the  vicinity  of  patients,  and  that  perhaps 
the  air  of  a  room  is  not  always  dangerous  to  breathe  even  if 
tubercle  bacilli  can  be  found  in  the  settled  dust. 

Pus-forming  Bacteria  in  Air.  —  Numerous  observers  are 
referred  to  by  Gotschlich,^  Friedrich*  and  Noeggerath^  as 

'  Cornet  and  Meyer,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena, 
1903,  II,  143. 

*  Le  Xoir  and  Camus,  Comp.  rend.  Soc.  de  biol.,  Par.,  1908,  LXV, 
464,  622;  Ann  d'hyg.  et  de  m6d.  colon.,  Par.,  1908,  4  s.,  IX,  74. 

'  Gotschlich, Kolle  u.Wa.ssormann,  Handhurh  [etc.),  Jena,  1902,1, 176. 

*  Friedrich,  Arch.  f.  klin.  Chir.,  Borl.,  1898,  LVII,  288. 

*  Noeggerath,  Deutsche  Ztschr.  f.  Chir.,  Lcipz.,  1900-01,  LVIII,  277. 


250       THE  SOURCES  AND  MODES  OF  INFECTION 

having  found  various  pus-forming  bacteria  in  the  wards  and 
operating  rooms  of  the  hospitals.  Among  more  recent  Ameri- 
can writers  may , be  mentioned  Robb,'  Rosenow,^  Monks  ^  and 
Harrington/  The  latter  found  that  Petri  dishes  exposed  in 
an  operating  room  in  Boston  always  contained  pus  organisms. 
The  maximum  was  131  per  square  inch  per  hour.  Gordon " 
found  staphylococci  in  an  operating  room  in  England,  also  in 
a  barber's  shop,  and  they  have  been  demonstrated  in  the  air 
by  Hamilton.®  Gordon  could  not  find  them  in  the  open  air, 
but  they  have  been  found  in  the  air  of  streets  by  others.^ 

Other  Bacteria  in  Air.  —  Concornotti  ^  reports  that  he 
found  pneumonia  germs  in  the  air  of  the  Hygienic  Institute 
of  Cagliari. 

Beck  ^  found  swine  plague  bacilli  in  the  air  of  a  laboratory 
where  experiments  with  that  germ  were  being  carried  on. 

Bruce  ^"  could  not  find  the  germ  of  Mediterranean  fever  in 
air-borne  dust  in  Malta. 

Actual  Danger  of  Infection  by  Air.  —  Pathogenic  bacteria 
may  withstand  drying  and  the  pulverization  of  the  dried 
material,  and  they  may  be  actually  found  floating  in  the  air, 
yet  they  may  not  after  all  be  dangerous,  either  because  they 
have  wholly  or  partially  lost  their  virulence,  or  because  they 
are  too  few  in  number,  or  for  some  other  unknown  reason. 

Little  Infection  of  Wounds  by  Air.  —  It  has  been  shown 
that  notwithstanding  the  presence  of  considerable  numbers 

'  Robb,  Am.  J.  Obst.,  N.  Y.,  1909,  LX,  451. 

2  Rosenow,  Am.  J.  Obst.,  N.  Y.,  1904,  L,  762. 

3  Monks,  Ann.  Surg.,  Phila.,  1904,  XL,  466. 

4  Harrington,  Ann.  Surg.,  Phila.,  1904,  XL,  475. 

5  Gordon,  Rep.  Med.  Off.  Local  Gov.  Bd.,  Lond.,  1904-05,  XXXIV, 
387. 

«  Hamilton,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  1108. 
^  Newman,  Bacteriology  and  the  Pub.  Health,  Lond.,  1904,  78. 
'  Concornotti,  Centrlbl.  f.  Bakteriol.  [etc.],  Jena,  1899,  XXVI,  492. 
®  Beck,  Jahresb.  u.  d.  Fortschr.  .   .   .  d.  path.  Mik.,  Baumgarten, 
1891,  VII,  567. 
"  Nature,  Lond.,  1908,  LXXVIII,  40. 


INFECTION  BY  AIR  251 

of  bacteria  in  the  air  of  operating  rooms,  the  aerial  infection 
of  wounds  is  of  no  practical  importance.  One  reason  for  this 
failure  to  infect  has  been  shown  by  Friedrich^  and  Noeg- 
gerath."  The  conclusion  of  these  authors  is  that  drying  and 
exposure  to  light  so  weaken  the  bacteria  that  they  are  not 
able  to  withstand  the  actively  hostile  influences  of  the  tissues 
of  the  human  body,  though  they  may  be  able  slowly  to  vege- 
tate on  the  more  favorable  culture  media  of  the  laboratory. 
This  lowering  of  virulence  by  drying  and  exposure  to  light 
may  be  of  great  practical  moment  in  preventing  infection  by 
air.  So  also,  though  other  pathogenic  bacteria  may  be 
demonstrated  in  the  air,  it  may  be  that  they  are  usually 
too  few  in  number  to  infect. 

Experiments  with  Tuberculosis.  —  The  experiment  of 
Bernheim,^  in  which  he  was  not  able  to  infect  animals  with 
mouth  spray  over  25  cm.  from  the  mouth,  but  was  able  to 
collect  tubercle  bacilli  on  agar  plates  at  the  distance  of  a 
meter,  is  most  suggestive  of  the  importance  of  the  number 
of  bacteria  as  a  factor  in  infection.  The  proper  way  to  de- 
termine the  infectivity  of  the  air  is  by  animal  experiment 
or,  better  still,  by  carefully  conducted  observations  on  human 
beings.  Except  in  tuberculosis  very  few  experiments  of  this 
kind  have  been  made.  Much,  however,  has  been  done  with 
that  disease. 

Tappeiner^  had,  even  before  the  discovery  of  the  tubercle 
bacillus,  shown  that  tuberculosis  could  be  produced  in  dogs 
by  causing  them  to  breathe  dry  and  pulverized  tuberculous 
sputum.  Bertheau,  Veraguth,  Weichselbaum  and  Frerich, 
like  Tappeiner,  succeeded  in  infecting  animals  by  causing 
them  to  inhale  pulverized  sputum  containing  tubercle  bacilli, 
while  Koch,  Cornet,  Gcbhardt  and  Preyss  accomplished  the 

1  Friedrirh,  Arch.  f.  klin.  Chir.,  Bcrl.,  1898,  LVII,  288. 

2  Noeggorath,  Deutsche  Ztsehr.  f.  Cliir.,  Ix^ipz.,  1000-01,  LVIII,  277. 
'  Hernheim,  ('linique,  Brux.,  190.5,  XIX,  340. 

*  Tappeiner,  Virchow's  Arch.  f.  path.  Anat.  [etcl,  Berl.,  1880, 
LXXXII,  353. 


252       THE  SOURCES  AND  MODES  OF  INFECTION 

same  results  by  the  use  of  dried  bacilli  obtained  from  cul- 
tures. More  recently  Cornet  ^  reports  a  still  more  striking 
experiment.  In  a  room  of  seventy-six  cubic  meters  capacity, 
48  guinea  pigs  were  exposed  in  cages  at  various  heights 
above  the  floor.  Sputum  was  placed  on  a  carpet,  and  after 
it  was  dry  the  carpet  was  shaken  so  that  the  dust  rose  up 
in  clouds.  This  was  repeated  on  four  days.  The  result  was 
that  47  of  the  48  animals  developed  tuberculosis  within  two 
months.  Kuss  "  carried  on  experiments  very  similar  to  those 
of  Cornet  and  with  similar  results.  Kohlisch,^  while  admit- 
ting that  tuberculosis  may  be  caused  by  the  inhalation  of  dust, 
claims  that  his  experiment  shows  that  enormously  larger 
quantities  must  be  inhaled  than  are  necessary  when  a  spray 
is  employed.  While  B.  prodigiosus  is  not  pathogenic,  it  has 
b*en  used  by  various  workers  for  studying  the  penetration 
of  bacteria  into  the  respiratory  tract.  Nenninger,^  using 
both  infected  dust  and  a  sprayed  culture,  found  that  the 
germs  were  quickly  carried  to  the  smallest  bronchioles. 

Dust  Infection  Questioned.  —  The  contention  that  pul- 
monary tuberculosis  may  be  caused  by  the  inhalation  of  dust 
containing  tubercle  bacilli  was  not  to  go  unchallenged.  Sirena 
and  Pernice,  de  Toma,  Celli  and  Guarnieri,  and  Cadeac  and 
Malet  were  unsuccessful  in  their  attempts  to  produce  the 
disease  in  this  way.  But  perhaps  Fliigge^  more  than  any 
other  has  cast  discredit  on  this  theory  of  the  origin  of  pul- 
monary tuberculosis.  He  was  unable  to  induce  infection  by 
causing  animals  to  inhale  tuberculous  dust,  and  states  that  the 
dust  is  not  carried  to  the  alveoli.  He  also  developed  the 
theory  of  droplet  infection,  which  has  been  received  with  much 

1  Cornet,  Verhandl.  d.  Berl.  med.  Gesellsch.,  1899,  XXX,  2  Th.,  91. 

2  Kuss,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  101. 

^  Kohlisch,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1908,  LX, 
508. 

*  Nenninger,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1901, 
XXXVIII,  94. 

^  Fliigge,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
107. 


INFECTION  BY  AIR  253 

favor,  and  did  much  to  break  down  the  almost  universal 
view  that  dust  is  the  chief  vehicle  of  infection  in  this  disease. 
Again  when  Koch  in  1901  by  his  pronunciamento,  that  human 
tuberculosis  is  never  caused  b}^  the  milk  of  tuberculous  ani- 
mals, stimulated  a  great  number  of  workers  to  attempt  to 
prove  the  contrarj-,  evidence  began  to  accumulate  that  tuber- 
culous infection  of  the  lungs  might  be  brought  about  in  vari- 
ous ways,  and  facts  came  to  light  which  told  against  the  view 
that  direct  infection  by  means  of  dust  is  the  only  manner 
in  which  pulmonary'  tuberculosis  can  be  caused. 

Dust  versus  Droplets.  —  According  to  the  school  of  Flligge, 
infection  by  droplets  is  much  more  likel}'  to  take  place  than 
infection  by  dust,  and  his  pupils  have  demonstrated  the 
presence  of  the  bacilli  in  the  lungs  immediately  after  inhala- 
tion. Findel,'  working  in  his  lal^oratory,  has  shown  that  the 
inhalation  of  even  so  small  a  number  as  62  germs  is  sufficient 
to  cause  the  disease,  and  he  asserts  that  several  million  times 
as  many  bacteria  are  necessary  to  infect  when  taken  by  the 
stomach.  Laschtschenko^  and  Heymann,^  working  under 
the  direction  of  Fliigge,  were  able  to  infect  guinea  pigs  with 
tuberculosis  by  causing  them  to  breath  directly  in  front  of  the 
mouth  of  phthisical  patients  while  the  latter  were  coughing. 
The  pigs  were  not  infected  when  distant  over  one  meter. 
Fliigge^  himself  infected  6  of  25  guinea  pigs  in  this  manner, 
holding  them  distant  from  twenty  to  fortj'-five  cm.  from  the 
mouth  of  the  patient.  Pfeiffer  and  Friedberger  ^  sprayed 
guinea  pigs  with  a  culture  containing  35,000  tubercle  bacilli  to 

'  Findel,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1907,  LVII, 
104. 

2  La.schtschenko,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Loipz.,  1899, 
XXX,  12.5. 

'  Heymann,  Zt.schr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
139. 

<  FlUggo,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1899,  XXX, 
107. 

"  Pfeiffer  and  Friedberger,  Deutsche  med.  Wchnschr.,  1907,  XXXIII, 
1577.  , 


254       THE  SOURCES  AND  MODES  OF  INFECTION 

the  c.c.  The  animals  were  held  for  ten  minutes  at  a  distance 
of  eight  to  twenty  cm.  in  such  a  manner  that  their  bodies 
were  perfectly  protected.  Those  held  at  the  greater  distance 
did  not  contract  tuberculosis,  but  the  others  developed  what 
appeared  to  be  primary  tuberculosis  of  the  lungs.  Bartel 
and  Neumann/  after  spraying  guinea  pigs  with  tubercle 
bacilli,  found  the  germs  immediately  in  mouth,  throat  and 
lungs.  Bernheim^  infected  guinea  pigs  at  the  distance  of 
not  over  twenty-five  cm.,  but  he  was  able  to  collect  tubercle 
bacilli  on  agar  plates  at  the  distance  of  one  meter  from  the 
mouth.  So  also  Kuss  and  Lobstein,^  carrying  out  very  care- 
ful inhalation  experiments  with  a  sprayed  culture  of  tubercle 
bacilli,  very  easily  and  constantly  developed  pulmonary 
disease.  Kovacs,*  after  inhalation  experiments  with  tubercle 
bacilli,  could  immediately  recover  them  from  the  lungs.  But 
he  thinks  that  they  may  also  pass  from  the  mouth  to  the 
lungs  via  the  cervical  and  bronchial  glands.  Cobbett,''  em- 
ploying sprays  both  of  B.  prodigiosus  and  of  the  tubercle 
bacillus,  reports  that  the  bacteria  are  carried  to  the  periph- 
ery of  the  lungs  by  the  inspired  air. 

The  Inhalation  of  Bacteria.  —  On  the  other  hand,  Hewlett 
and  Thompson  ®  found  that  inhaled  bacteria  were  not  carried 
even  as  far  as  the  trachea,  as  Hildebrandt  ^  had  found  before. 
Hartl  and  Herrmann^  showed  that  inhaled. germs  decreased 
very  rapidly  back  from  the  nose,  and  they  consider  that  the 
upper  passages  are  frequently  the  place  of  entrance  for  the 
infection,  and  that  bacteria  are  rarely  carried  by  the  air  to 

1  Bartel  and  Neumann,  Wien.  klin.  Wchnschr.,  1906,  XIX,  167,  213. 

2  Bemheim,  Clinique,  Brux.,  1905,  XIX,  346. 

'  Kuss  and  Lobstein,  Bull,  med.,  Paris,  1907,  XXI,  821. 

^  Kovdcs,  Beitr.  z.  path.  Anat.  u.  z.  allg.  Path.,  Jena,  1906,  XL,  281. 

»  Brit.  M.  J.,  Lond.,  1909,  II,  867. 

^  Hewlett  and  Thompson,  Lancet,  Lond.,  1896,  I,  86. 

^  Hildebrandt,  Beitr.  z.  path.  Anat.  u.  z.  allg.  Path.,  Jena,  1887,  II, 
411. 

*  Hartl  and  Herrmann,  Wien.  klin.  Wchnschr.,  1905,  XVIII,  798. 


INFECTION  BY  AIR  255 

the  lungs.  Vallee  ^  carried  on  spray  experiments  without 
result,  and  Calmette  and  Guerin,^  in  a  few  experiments  made 
with  infected  dust,  did  not  find  that  the  bacilli  reached  the 
alveoli.  Weleminsky^  could  find  no  bacilli  in  the  lungs  of 
guinea  pigs  immediately  after  they  had  been  subjected  to 
inhalation  experiments. 

Lack  of  Agreement  among  Investigators.  —  Thus  it  is  seen 
that  the  school  of  Cornet  claims  that  pulmonary  tuberculosis 
is  almost  always  caused  by  the  passage  of  infected  dust  to  the 
alveoli,  and  that  infected  droplets  are  of  little  moment;  while 
Fliigge  and  his  pupils  attempt  to  show  that  dust  rarely  reaches 
the  alveoli  but  that  the  inhalation  of  droplets  is  the  easiest 
method  of  causing  the  disease.  The  unprejudiced  reader 
must  conclude  that  infection  in  either  way  is  possible,  but 
the  conditions  of  the  experiments  are  so  far  removed  from  the 
natural  that  there  must  be  much  hesitation  before  assuming 
that  this  work  indicates  in  any  degree  the  common  mode  of 
infection  in  human  beings. 

Bacilli  may  pass  from  Stomach  to  Lungs.  —  It  is  com- 
monl}^  assumed  that  because  pulmonary  tuberculosis  begins 
in  the  apices  of  the  lungs  the  bacilli  must  be  carried  directly 
to  the  alveoli  by  the  inspired  air.  Moreover  most  patholo- 
gists consider  that  evidence  points  to  the  alveolar  surface  as 
the  starting  point  of  the  disease,  and  that  the  relative  age  of 
the  lesions  in  the  lungs  and  the  glands  indicates  that  it  is 
primarily  a  pulmonary  disease.  The  writer  is  not  competent 
to  discuss  the  findings  of  the  pathologists,  but  there  are  a 
large  number  of  careful  observers  who  believe  on  pathological 
and  experimental  evidence  that  the  bacilli  which  cause  pul- 
monary tuberculosis  may  find  their  way  through  the  lymph 
and  the  blood  from  any  part  of  the  alimentary  tract  to  the 
lungs.  Some  pathologists  believe  that  the  disease  begins 
in  the  capillaries  rather  than  in  the  alveoli.     Calmette  and 

1  Vall6e,  Ann.  d.  I'ln-st.  Pasteur,  190.5,  XIX,  G19. 

*  Calmette  and  Guerin,  Ann.  de  I'ln.st.  Pasteur,  1905,  XIX,  601. 

»  Weleminsky,  Berl.  klin.  Wchnschr.,  1905,  XLII,  743. 


256       THE  SOURCES  AND  MODES  OF  INFECTION 

Guerin  ^  say  that  primary  tubercle  of  the  lungs  always  be- 
gins in  the  capillaries,  and  never  in  the  alveoli,  and  Aufrecht  ^ 
from  his  pathological  studies  comes  to  the  same  conclusion. 

Even  pulmonary  anthracosis  may  be  caused  by  the  inges- 
tion of  particles  of  carbon.  Vansteenburgh  and  Grysez  ^ 
caused  animals  to  breath  air  loaded  with  soot  from  a  smoky 
lamp,  and  though  the  nose  was  filled  with  soot,  none  was  found 
in  lungs  or  even  trachea.  If  the  experiment  was  prolonged, 
carbon  appeared  in  the  lungs,  but  not  if  the  esophagus  was  tied. 
When  one  bronchus  was  occluded,  the  carbon  appeared  in  the 
parenchyma  of  the  lung  just  the  same,  provided  the  esoph- 
agus was  open.  Whitla*  fed  animals  with  carbon  and  baciUi, 
and  both  were  found  in  the  lungs  in  from  four  to  twenty-four 
hours.  Feeding  was  done  with  a  tube,  with  great  care  to 
prevent  inhalation.  Hutchens ''  fed  guinea  pigs  with  coal 
dust,  and  also  injected  it  into  the  abdomen,  and  found  it  in 
the  lungs  in  three  days.  Grober,*^  after  injecting  India  ink 
into  the  tonsils,  was  able  to  find  the  pigment  in  the  lungs 
in  a  short  time.  He  thought  that  he  could  trace  a  continu- 
ous lymphatic  route  from  the  tonsils  to  the  costal  pleura, 
whence  the  particles  passed  directly  to  the  parietal  pleura 
and  the  lungs.  But  such  a  connection  has  been  denied  by 
Beitzke,^  Wood  ^  and  others. 

Schultze  ^  denies  that  pulmonary  anthracosis  can  be  pro- 

1  Calmette  and  Guerin,  Ann.  de  I'Inst.  Pasteur,  1906,  XX,  609. 

2  Aufrecht,  Deutsches  Arch.  f.  klin.  Med.,  Leipz.,  1908,  XCIV,  308. 
'  Vansteenburgh  and  Grysez,  Ann.  de  I'Inst.  Pasteur,  1905,  XIX,  787. 

*  Whitia,  Brit.  M.  J.,  Lond.,  1908,  II,  61. 

6  Cited  by  Ohver,  Brit.  M.  J.,  Lond.,  1908,  II,  481. 

*  Grober,  Die  Tonsillen  als  Eintrittspforten  fiir  Krankheitserreger, 
Abdruck  aus  dem  klin.  Jahrb.,  Berl.,  1905,  XIV,  547. 

'  Beitzke,  Virchow'sArch.f.  path.  Anat.  [etc.],  Berl.,  1906,  CLXXXIV, 
1;  Berl.  klin.  Wchnschr.,  1908,  XLV,  1235. 

*  Wood,  Rep.  Henry  Phipps  Inst.  Study  .  .  .  Tuberculosis,  Phila., 
1906,  IV,  163. 

'  Schultze,  Miinchen  med.  Wchnschr.,  1906,  LIII,  1702. 


INFECTION  BY  AIR  2bl 

duced  by  feeding,  as  is  claimed  by  the  French  experimenters, 
and  insists  that  during  the  feeding  some  inhalation  takes  place, 
and  that  if  the  animals  are  fed  through  a  gastric  fistula  with 
adequate  precautions,  the  fragments  are  not  carried  to  the 
lungs. 

A  large  number  of  workers  have  certainly  demonstrated 
that  pulmonary  tuberculosis  may  be  caused  by  infection 
through  different  portions  of  the  alimentary  canal. 

The  work  of  Calmette  and  Guerin  ^  shows  that  tubercle 
bacilli  are  speedily  carried  from  the  intestines  to  the  lungs. 

Schroeder  and  Cotton"  have  shown  that  pulmonary  disease 
develops  no  matter  in  what  part  of  the  body  tubercle  bacilli 
are  inoculated,  and  in  Bulletin  88  they  have  shown  that 
marked  pulmonary  invasion  occurs  constantly  in  hogs  fed  on 
tuberculous  material.  So  also  Ravenel  ^  has  recovered  tu- 
bercle bacilli  from  the  lungs  within  a  few  hours  after  placing 
them  in  the  stomach  by  celiotomy.  Beitzke  ^  in  a  review  of 
the  subject  states  that  Schlossmann  and  St.  Engel"  found  the 
bacilli  in  the  lungs  six  hours  after  injection  into  the  stomach 
by  laparotomy,  as  did  also  L.  Rabinowitsch,  and  that  the 
latter  and  also  Uffenheimer,  Bacharach,  and  Stein  and  Orth 
found  them  after  injection  into  the  intestine.  Ficker,  he  says, 
could  not  do  this  with  adult  dogs  or  cats,  and  Herrmann  could 
not  with  monkeys.  Vallee,''  Calmette  and  Guerin,*  Bonome  ^ 
and  Arloing  **  also  have  demonstrated  pulmonary  infection 

1  Calmette  and  Gudrin,  Ann.  de  I'lnst.  Pasteur,  1905,  XIX,  601; 
1906,  XX,  353,  609. 

»  Schroeder  and  Cotton,  U.  S.  Dept.  Agric.  Bu.  An.  Ind.  Bull.  No.  86 
and  No.  93. 

'  Ravenel,  Cleveland  M.  J.,  1909,  VIII,  179. 

<  Beitzke,  Berl.  klin.  Wchnschr.,  1908,  XLV,  1235. 

*  Schlossmann  and  St.  Engel,  Deutsche  med.  Wchnschr.,  1906, 
XXXII,  1070. 

«  Vallee,  Ann.  dc  I'ln.st.  Pa-steur,  1905,  XIX,  619. 

'  Bonome,  Gazz.  d.  osp.,  Milano,  HK)7,  XXVIII,  Xos.  37-84,  abstract 
in  J.  Am.  iM.  A.s.s.,  Chicago,  1907,  XLIX,  888. 

"  Arloing,  Si.xth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  IV,  666. 


258       THE  SOURCES  AND  MODES  OF  INFECTION 

via  the  alimentary  tract,  and  very  many  of  the  experiments 
have  shown  that  the  bacilli  easily  pass  through  the  intestinal 
wall  without  leaving  a  trace  of  their  passage,  so  that  the 
absence  of  lesion  of  the  alimentary  tract  is  no  proof  that 
infection  has  not  taken  place  through  it. 

Unnatural  Conditions  of  Experiment.  —  Although  there 
has  been,  as  is  here  shown,  a  vast  amount  of  experimental 
work  on  infection  with  tuberculosis,  there  has  been  very  little 
in  which  the  conditions  at  all  approached  the  natural.  Usu- 
ally there  is  an  excessive  amount  of  exposure,  or  an  excessive 
number  of  germs  in  spray  or  dust.  Thus  in  Cornet's  nota- 
ble experiment,  where  47  of  48  guinea  pigs  were  infected  by 
breathing  dust,  the  carpet  had  been  smeared  with  large 
quantities  of  sputum,  and  it  was  forcibly  beaten  so  that 
clouds  of  dust  rose  up  directly  in  front  of  the  animals.  It  is 
surprising  that  so  few  have  thought  it  worth  while  to  see 
how  infection  takes  place  in  animals  kept  under  conditions 
as  nearly  as  possible  like  those  under  which  human  beings 
live. 

Infection  in  Laboratory.  —  Animals  kept  in  laboratories  in 
company  with  others  that  have  been  purposely  infected  rarely 
contract  the  disease.  Koch^  in  his  original  paper  says  that 
among  the  hundreds  of  animals  so  kept  the  disease  did  not 
develop  for  three  or  four  months,  and  then  only  exception- 
ally. He  reports  autopsies  on  17  guinea  pigs  and  8  rabbits 
thus  naturally  infected,  which  showed  in  all  cases  a  pul- 
monary tuberculosis  resembling  that  which  occurs  in  man. 
But  apparently  no  effort  was  made  to  determine  whether 
infection  was  by  the  air,  by  the  food,  or  by  contact  through 
the  hands  of  attendants,  though  this  laboratory  infection  has 
been  urged  as  evidence  that  the  disease  is  air-borne.  Of  many 
hundreds  of  guinea  pigs  confined  in  a  room  with  various 
tuberculous  animals  in  the  Department  of  Agriculture  Ex- 
periment Station  at  Washington,  only  one  contracted  tuber- 

1  Koch,  Mit.  a.  d.  k.  Gesund.-Amt.,  1884,  II,  Trans.  Sydenham  Soc. 
Pub.,  CXV,  129. 


INFECTION  BY  AIR  259 

culosis,  and  that  was  in  a  cage  with  several  infected  animals.^ 
In  laboratories  floating  bacteria  are  not  likely  to  be  very  nu- 
merous, owing  to  the  cleanliness  practiced  and  the  fact  that 
most  of  the  laboratory  animals  do  not  excrete  many  Vjacilli. 
Experiments  under  Natural  Conditions.  Tuberculosis.  — 
Schroeder  and  Cotton"  experimented  under  more  natural 
conditions.  Seven  cows  were  exposed  in  adjoining  stalls  to 
3  tuberculous  animals,  and  all  but  1  of  them  contracted  the 
disease.  As  all  but  2  were  moved  about  from  stall  to  stall, 
exchanging  with  the  infected  animals,  infection  may  readily 
have  been  by  contact.  At  the  same  time  100  guinea  pigs 
were  exposed  in  the  stalls,  one  half  in  cages  below  the  man- 
gers where  food  could  sift  through  from  the  mangers,  and 
one  half  on  the  walls.  The  exposure  lasted  several  months, 
and  only  1  of  the  pigs,  in  a  cage  under  the  manger,  became 
infected.  In  a  subsequent  experiment  35  guinea  pigs  w^ere  ex- 
posed for  one  hundred  and  thirty-five  days  on  the  w'alls  of 
the  stalls.  Two  developed  generalized  tuberculosis.  Of  42 
animals  kept  for  fifty-one  days  under  the  manger  of  infected 
cows,  6  developed  a  more  or  less  generalized  type  of  the 
disease.  There  was  no  direct  evidence  that  tubercle  bacilli 
were  in  the  air  of  the  stalls,  but  as  the  infecting  animals 
were  excreting  large  numbers  of  bacilli,  there  is  little  doubt 
of  it.  There  is  no  record  that  contact  infection  from  the 
hands  of  attendants  was  strictly  guarded  against,  and  it  may 
be  that  the  2  out  of  135  guinea  pigs,  and  the  2  cows  supposed 
to  have  succumbed,  to  air-borne  infection,  were  really  infected 
by  contact.  Swenson,  quoted  by  Aufrecht,  exposed  five 
calves  in  a  stable  with  tuberculous  cows  in  such  a  manner  as 
to  preclude  contact  infection,  and  they  all  developed  the 
disease,   as   Swenson   thought,  by  dust  infection.      Klein  ^ 

»  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  Wash.,  1906,  XXIII,  31. 

*  Schrooder  and  Cotton,  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind., 
Wash.,  1903,  XX,  61;  1904,  XXI,  44,  reprinted  as  Circ.  No.  83. 

*  Stevenson  and  Murphy,  Treatise  on  Hygiene  and  Public  Health, 
Load.,  1893-96,  II,  212. 


260       THE  SOURCES  AND  MODES  OF  INFECTION 

exposed  guinea  pigs  in  the  vent  shaft  of  the  Brompton  Hos- 
pital, and  most  of  them  contracted  tuberculosis. 

Experiments  in  Tuberculosis  Houses.  —  Bartel  and  Spieler/ 
realizing  that  most  experiments  are  under  unnatural  con- 
ditions, exposed  12  guinea  pigs  in  cages  in  a  house  occupied 
by  tuberculous  patients,  and  allowed  16  to  run  at  large  and 
be  handled  by  the  children.  The  exposure  was  from  two  to 
three  weeks,  and  of  the  12  cage  pigs  3  developed  tubercu- 
losis, and  of  the  16  free  pigs  10  developed  tuberculosis  of 
various  glands  and  other  organs.  No  statement  is  made 
that  care  was  taken  to  prevent  contact  or  mouth-spray  in- 
^  fection  of  the  animals  in  the  cages.  These  authors  ^  exposed 
8  guinea  pigs,  running  free,  in  a  house  where  the  tuberculous 
patient  was  taking  fairly  good  care  of  the  sputum.  Only  1 
of  the  guinea  pigs  developed  tuberculosis. 

At  my  suggestion  Dr.  M.  S.  Packard  of  Providence  carried 
on  an  experiment  for  the  health  department  of  that  city  on 
the  mode  of  infection  of  guinea  pigs  under  natural  conditions. 
A  fairly  clean  laborer's  house  was  chosen,  where  there  was  a 
consumptive  whose  sputum  contained  large  numbers  of  ba- 
cilli, and  who  was  taking  no  care  whatever  in  regard  to  its 
disposal.  Thirty-six  small  guinea  pigs  were  exposed  in  cages 
placed  in  a  dark  place  in  the  room  in  which  the  patient  usually 
sat.  The  cages  were  much  crowded.  Of  the  animals,  16 
were  fed  and  cared  for  by  the  consumptive,  and  the  others 
by  an  employee  of  the  department  free  from  disease.  These 
latter  animals  were  locked  in  a  box  covered  with  wire  net- 
ting, fourteen  meshes  to  the  inch.  There  could  be  no  ques- 
tion of  contact  infection  for  these  pigs.  The  exposure  was 
from  February  11,  1908,  to  May  14.  All  but  21  of  the 
animals  died  of  non-tuberculous  disease,  or  were  starved  or 
killed  by  rats  after  removal  from  the  house.  Of  the  11 
surviving  animals  exposed  to  air  infection  alone,   8  were 

1  Bartel  and  Spieler,  Wien.  klin.  Wchnschr.,  1905,  XVIII,  218. 
^  Festschr.  enthalt.  Arb.  u.  Tuberk.  ...  VI  Internat.  Tuberk.  Konf. 
[etc.],  Wien  u.  Leipz.,  1907,  71. 


INFECTION  BY  AIR  261 

shown  to  be  tuberculous  and  3  not  tuberculous.  Of  the 
other  lot,  7  were  shown  to  be  tuberculous  and  3  not.  It 
seems  impossible  that  the  test  animals  could  have  been  in- 
fected otherwise  than  through  the  air.  That  it  was  mouth 
spray  rather  than  dust  infection  seems  likely,  for  the  patient 
took  much  interest  in  the  animals,  and  was  often  seen  with 
his  face  close  to  the  netting,  talking  to  them,  and  coughing  at 
them  only  a  few  inches  distant.  The  guinea  pigs  were  pur- 
chased, but  I  was  unable  to  learn  that  they  had  ever  been 
exposed  to  the  disease. 

Since  writing  the  above  I  note  that  Le  Noir  and  Camus  ^ 
have  undertaken  a  similar  experiment.  They  exposed  guinea 
pigs  in  cages  in  a  ward  for  phthisical  patients.  Four  pigs 
were  placed  in  a  cage  on  the  floor  and  the  patients  fed  these. 
One  of  them  developed  tuberculosis.  Five  pigs  were  kept 
for  six  weeks  in  a  cage  on  the  floor  but  protected  so  that  the 
patients  could  not  reach  them.  One  of  these  also  developed 
tuberculosis.  Another  pig  with  three  little  ones  was  placed 
in  a  cage  near  the  ceiling  so  that  they  had  to  be  fed  from  a 
ladder.  One  of  the  little  ones  died  of  an  intercurrent  affec- 
tion, but  the  other  two  contracted  tuberculosis. 

Since  it  is  claimed  by  the  majority  of  those  interested  in 
tuberculosis  that  the  disease  is  spread  chiefly  by  means  of 
dust,  it  is  highly  desirable  that  a  sufficient  numl^er  of  well- 
conducted  experiments  under  trul}'  natural  conditions  be 
made  to  determine  how  important  this  mode  of  infection 
really  is. 

Except  for  tuberculosis  very  little  animal  experimentation 
has  been  done  to  determine  whether  diseases  are  air-borne. 
One  reason  for  this,  of  course,  is  that  so  many  of  the  com- 
moner diseases  affecting  human  beings  are  not  easily  con- 
tagious for  the  lower  animals. 

Experiments  with  Mediterranean  Fever.  —  Horrocks,' 
experimenting  with    monkeys,   could    cause  Mediterranean 

'  IjQ  Noir  and  Camus,  Presse  mdd.,  Par.,  1909,  XVII,  761. 
*  Horrocks,  Report  of  Royal  Commission  on  Malta  Fever. 


262       THE  SOURCES  AND  MODES  OF  INFECTION 

fever  by  making  the  animals  inhale  dust  artificially  infected 
with  large  numbers  of  M.  melitensis,  but  he  was  not  successful 
with  dust  naturally  infected  with  urine,  though  the  organism 
of  this  disease  is  very  resistant  to  drying.  Monkeys  kept  in 
cages  near  infected  animals  did  not  contract  the  disease, 
unless  there  was  actual  contact  with  infected  material,  i.e., 
there  was  no  air-borne  infection.  Epidemiological  evidence 
is  against  this  being  a  dust  disease,  for  it  prevails  far  less 
during  the  dry  than  during  the  wet  season.  That  it  is  in 
reality  exclusively  milk-borne  seems  now  to  have  been 
demonstrated. 

Experiments  with  Anthrax.  —  Biichner  ^  was  the  first  to 
attempt  to  infect  animals  by  making  them  breathe  dried 
anthrax  bacilli  or  spores.  He  easily  succeeded  in  thus  caus- 
ing primary  pulmonary  disease.  Miiskatbltith  ^  showed  that 
the  spores  would  readily  pass  the  lungs  without  causing  local 
disease.  Morse,  Hildebrandt,  Tschistovitsch  and  Gramat- 
schikoff  ^  could  not  cause  the  disease  by  inhalation  even 
when  the  spray  was  sent  directly  into  the  trachea.  Baum- 
garten*  believes  that  these  various  experiments  show  that 
infection  takes  place  by  the  tonsils  rather  than  directly  by 
the  lungs. 

Experiments  with  Plague.  —  Bubonic  plague  is  often  con- 
sidered an  air-borne  disease,  but  the  experiments  of  the  present 
Indian  Plague  Commission^  have  shown  that  this  is  not  the 
case.  Both  monkeys  and  guinea  pigs  have  in  considerable 
numbers  been  put  in  flea-proof  cages,  but  exposed  freely  to 
the  air,  and  the  cages  placed  in  dwellings  known  to  be  in- 
fected, and  in  no  instance  did  they  contract  the  disease.  In 
other  instances  the  animals  were  exposed  freely  to  the  air,  but 

1  Biichner,  Centrlbl.  f.  Bakteriol.  [etc.],  Jena,  1890,  VII,  733; 
VIII,  1. 

2  Muskatbliith,  Centrlbl.  f.  Bakteriol.  [etc.],  Jena,  1887,  I,  321. 

'  ^  Cited  by  Sobernheim  in  Kolle  u.  Wassermann  Handbuch  [etc.], 
Jena,  1903,  II,  49. 

*  Lehrbuch  der  Pathologischen  Mycologie,  Braunschweig,  1890. 

5  Journal  Hygiene,  1905,  835;  1906,  445-471;  1907,  432,  835,  979. 


INFECTION  BY  AIR  263 

were  protected  from  fleas  by  "  tangle-foot,"  with  like  results. 
These  experiments  were  made  at  various  times  and  places, 
but  the  animals  never  succumbed  to  air-borne  infection.  In 
all  instances  control  animals  not  protected  from  fleas  usually 
contracted  the  disease. 

Conclusions.  —  After  the  foregoing  survey  of  the  subject 
we  are,  I  think,  justified  in  the  following  conclusions: 

1.  The  theory  of  the  aerial  transmission  of  disease  was 
developed  as  the  most  reasonable  way  of  explaining  the  phe- 
nomena of  infection. 

2.  Contact  infection  with  carriers  and  missed  cases  affords 
a  better  explanation  of  the  phenomena. 

3.  The  best  medical  thought  has  been  steadily  restricting 
the  supposed  sphere  of  aerial  transmission. 

4.  Only  a  few  authorities  now  assert  that  disease  is  carried 
by  the  atmosphere  outside  of  dwellings,  and  this  assertion  is 
made  only  in  regard  to  smallpox, 

5.  Bacteriology  teaches  that  former  ideas  in  regard  to  the 
manner  in  which  diseases  may  be  air-borne  are  entirelj^  erro- 
neous; that  most  diseases  are  not  likely  to  be  dust-borne, 
and  they  are  spray-borne  only  for  two  or  three  feet'a  phe- 
nomenon which  after  all  resembles  contact  infection  more 
than  it  does  aerial  infection  as  ordinarily  understood. 
Tuberculosis  is  more  likely  to  be  air-borne  than  is  any  other 
common  disease. 

6.  Surgeons  at  first  developed  aseptic  surgery  on  the  theory 
that  air  infection  was  of  the  highest  importance.  They  have 
gradually  learned  to  pay  less  attention  to  it,  until  at  present 
some  of  the  best  surgeons  consider  it  a  negligible  factor, 

7.  Animal  experimentation  indicates  that  tuberculosis  and 
anthrax  may  be  air-borne,  and  that  plague  and  some  other 
tliseases  are  not. 

8.  Pathology  has  not  determined,  as  is  sometimes  alleged, 
that  even  pulmonary  consumption  is  an  air-borne  disease. 

9.  There  is  no  good  clinical  evidence  that  the  common 
diseases  are  air-borne. 


264       THE  SOURCES  AND  MODES  OF  INFECTION 

10.  There  is  considerable  clinical  evidence  that  scarlet 
fever,  diphtheria,  smallpox,  measles,  whooping  cough,  typhoid 
fever  and  plague  are  not  easily  transmissible  through  the  air. 

11.  Scarlet  fever  and  diphtheria  can  be  cared  for  in  the 
same  ward  with  other  diseases  without  extension,  if  clean- 
liness be  maintained  and  infection  by  contact  avoided. 

In  reviewing  the  subject  of  air  infection  it  becomes  evident 
that  our  knowledge  is  still  far  too  scanty,  and  that  the  avail- 
able evidence  is  far  from  conclusive.  Yet  it  is  of  the  greatest 
practical  importance  that  we  should  know  definitely  just  what 
danger  there  is  of  air-borne  infection  and  in  what  diseases 
it  is  to  be  feared.  Infection  by  air,  if  it  does  take  place,  as  is 
commonly  believed,  is  so  difficult  to  avoid  or  guard  against, 
and  so  universal  in  its  action,  that  it  discourages  effort  to 
avoid  other  sources  of  danger.  If  the  sick-room  is  filled  with 
floating  contagium,  of  what  use  is  it  to  make  much  of  an  effort 
to  guard  against  contact  infection  ?  If  it  should  prove,  as  I 
firmly  believe,  that  contact  infection  is  the  chief  way  in  which 
the  contagious  diseases  spread,  an  exaggerated  idea  of  the 
importance  of  air-borne  infection  is  most  mischievous.  It  is 
impossible,  as  I  know  from  experience,  to  teach  people  to 
avoid  contact  infection  while  they  are  firmly  convinced  that 
the  air  is  the  chief  vehicle  of  infection. 

While  it  is  not  possible  at  present  to  state  with  exactness 
the  part  played  by  aerial  infection  in  the  transmission  of  the 
different  infectious  diseases,  we  are  by  the  evidence  forced  to 
the  conclusion  that  the  current  ideas  in  regard  to  the  impor- 
tance of  infection  by  air  are  unwarranted.  Without  denying 
the  possibility  of  such  infection,  it  may  be  fairly  affirmed 
that  there  is  no  evidence  that  it  is  an  appreciable  factor  in 
the  maintenance  of  most  of  our  common  contagious  diseases. 
We  are  warranted,  then,  in  discarding  it  as  a  working  hy- 
pothesis and  devoting  our  chief  attention  to  the  prevention 
of  contact  infection.  It  will  be  a  great  relief  to  most  persons 
to  be  freed  from  the  specter  of  infected  air,  a  specter  which 
has  pursued  the  race  from  the  time  of  Hippocrates,  and  we 


INFECTION  BY  AIR  265 

may  rest  assured  that  if  people  can  as  a  consequence  be 
better  taught  to  practice  strict  personal  cleanliness,  they  will 
be  led  to  do  that  which  will  more  than  anything  else  prevent 
aerial  infection  also,  if  that  should  in  the  end  be  proved  to  be 
of  more  importance  than  now  appears. 


CHAPTER  VII. 

INFECTION    BY    FOOD   AND    DRINK. 

Infection  by  Water. 

Broad  Street  Well. — From  time  immemorial  water  has  been 
believed  to  be  the  bearer  of  disease,  but  it  is  only  since  the 
middle  of  the  nineteenth  century  that  the  subject  has  been 
scientifically  studied.  One  of  the  first  instances  of  a  clear- 
cut  demonstration  of  the  causation  of  sickness  by  infected 
water  was  that  of  the  now  famous  Broad  Street  well,  so  ably 
studied  by  Snow.^  During  the  outbreak  of  cholera  in  Lon- 
don in  1854  there  was  an  enormous  concentration  of  cases 
in  a  very  limited  area  just  east  of  Regent  Street,  there  having 
been  reported,  during  a  period  of  about  six  weeks,  over  600 
fatal  cases.  A  careful  study  of  the  site,  soil,  subsoil,  streets, 
density  and  character  of  population,  dwellings,  yards,  closets, 
cesspools,  vaults,  drains,  conditions  of  cleanliness  and  atmos- 
pheric conditions,  revealed  nothing  of  interest.  But  a  study 
of  the  water  supply  discovered  most  interesting  facts.  Nearly 
all  of  the  cases  were  nearer  a  certain  public  pump  in  Broad 
Street  than  any  other  well,  and  most  of  them  gave  a  definite 
history  of  getting  water  from  this  pump.  Of  the  very  few 
cases  (ten  at  the  time  of  the  investigation)  outside  of  the 
area  supplied  by  this  pump,  half  were  known  to  drink  water 
from  Broad  Street.  There  were  also  several  cases  of  cholera 
in  distant  parts  of  London  in  persons  who  drank  water  from 
this  well.  In  the  workhouse  with  535  inmates,  in  the  midst 
of  this  district,  but  with  its  own  well,  there  were  only  5 
deaths,  less  than  one-tenth  the  rate  in  the  neighborhood,  and 

^  Sedgwick,  The  Principles  of  Sanitary  Science  and  the  Public 
Health,  New  York,  1902,  170. 

266 


INFECTION  BY  FOOD  AND  DRINK  267 

in  a  brewery  with  70  employees  and  using  its  own  well  there 
was  not  a  single  case.  It  was  also  shown  that  a  privy  vault 
and  cesspool  in  the  adjoining  house  discharged  through  a  leaky 
drain  which  ran  within  two  feet  of  the  well.  There  were  4 
fatal  cases  of  cholera  in  this  house  at  the  time  of  the  outbreak 
and  obscure  earlier  cases  which  were  not  unlikely  cholera 
also. 

North  Boston  Well.  —  In  the  United  States  the  outbreak 
of  tj'phoid  fever  at  Xorth  Boston,  N.  Y.,  in  1843,  referred  to 
by  Flint  in  his  popular  text-books,  did  much  to  call  attention 
to  drinking  water  as  a  factor  in  the  spread  of  disease.  A 
young  man  from  Massachusetts  went  to  the  hamlet  sick  with 
typhoid  fever,  and  died  there.  He  lodged  at  the  tavern  where 
there  was  a  well  of  water  used  by  6  of  the  neighboring  fam- 
ilies. One  near-by  family  and  2  distant  families  did  not 
use  the  water  and  had  no  illness.  In  the  other  families  which 
did  use  the  water  there  were  28  cases  with  10  deaths.^ 

Recent  Studies.  —  Such  striking  demonstration  in  a  few 
instances  of  the  spread  of  disease  through  the  medium  of 
drinking  water  led  to  unwarranted  generalization,  and  during 
the  last  half  of  the  nineteenth  century  it  was  the  common 
belief  of  health  officials  and  medical  men  that  infected  water 
was  the  chief  factor  in  the  causation  of  typhoid  fever  and 
cholera,  and  that  it  was  of  great  importance  in  malaria,  yellow 
fever,  dysentery,  diarrhea,  and  was  perhaps  of  moment  in  all 
the  "  zymotic  "  diseases.  The  discovery  of  the  specific  organ- 
isms of  these  diseases,  and  the  application  of  more  scientific 
methods  to  their  study,  has  of  late  shown  that  water,  while 
a  factor  of  very  great  importance,  is  not  so  important  as  was 
at  one  time  supposed.  Let  us  consider  its  relation  to  specific 
di.seases. 

Typhoid  Outbreaks.  —  For  dwellers  in  temperate  regions 

typhoid  fever  is   the  most  important   water-borne   disease. 

The  demands  of  modern  civilization  require  for  the  constantly 

increasing  urban   population    a   pipe-distributed    municipal 

•  Am.  Pub.  Health  Ass.  Rep.,  187.3,  I,  167. 


268        THE  SOURCES  AND  MODES  OF  INFECTION 

supply  which  in  numerous  instances  must  be  taken  from 
streams  or  lakes  more  or  less  contaminated  with  sewage. 
The  plentiful  use  of  water  rendered  possible  by  a  municipal 
supply  produces  a  large  amount  of  sewage,  which  in  the  past 
has  usually  discharged  into  the  nearest  watercourse,  thus 
carrying  danger  to  any  other  community  which  might  become 
a  user  of  the  water.  From  what  is  known  of  the  life  history 
of  the  typhoid  bacillus  it  is  not  surprising  that  in  some  cities 
great  explosive  outbreaks  of  the  disease  have  been  caused  by 
a  temporary  pollution,  and  other  cities,  owing  to  continuous 
pollution  of  their  source  of  supply,  have  suffered  from  a  con- 
tinuous high  death  rate  from  this  disease.  The  former  class 
of  outbreaks,  while  in  the  aggregate  less  destructive,  are  most 
impressive  lessons  for  the  public  and  have  been  exceedingly 
instructive  to  the  epidemiologist.  The  demonstration  of  a 
water-borne  outbreak  depends  primarily  upon  statistics.  If 
there  is  an  excess  of  typhoid  fever  among  the  users  of  a  certain 
water  over  the  neighboring  population  living  under  the  same 
conditions  but  using  a  different  water,  and  if  other  sources, 
as  food  and  milk,  are  excluded,  the  outbreak  is  probably 
water-borne.  The  more  closely  the  users  and  non-users  of 
the  water  are  commingled,  and  the  greater  the  difference  in 
the  incidence  of  the  disease  upon  them,  the  more  certain  is  the 
demonstration.  During  the  outbreak  in  Scranton,  1906-07,^ 
there  were  four  separate  sections  of  the  city  not  supplied 
from  the  infected  reservoir  in  which  there  was  very  little 
typhoid,  and  most  of  the  cases  which  did  occur  in  these  dis- 
tricts were  shown  to  have  used  the  infected  water  in  other 
places,  or  to  have  been  subject  to  contact  infection.  In 
Paris,^  owing  to  partial  failure  of  the  good  supply,  the  im- 
pure Seine  water  was  turned  on  to  one  arrondissement  after 
another,  with  the  result  that  a  well-defined  epidemic  followed 
in  each  instance.  In  Philadelphia  the  gradual  introduc- 
tion of  filtered  water  has  resulted  in  a  decrease  in  typhoid 

1  Wainwright,  N.  York  M.  J.,  1907,  LXXXV,  1027. 
«  Jordon,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  1669. 


INFECTION  BY  FOOD  AND  DRINK  269 

fever,  limited  to  those  districts  to  which  the  water  has  been 
supphed. 

These  water-borne  outbreaks  are  usually  explosive  in  char- 
acter and  are  frequently  of  short  duration.  An  inspection  of 
the  supply  not  rarely  shows  that  the  feces  of  typhoid  cases 
have  entered  the  water  shortly  before  the  outbreak.  Such 
outbreaks  are  apt  to  occur  in  the  spring  when  the  freshets 
wash  the  surface  of  the  ground  into  the  streams.  The  bacilli 
have  rarely  been  found  in  the  incriminated  water. 

While  studying  this  subject  in  1888/  I  was  able  to  find 
thirteen  recorded  instances  of  the  recovery  of  typhoid  bacilli 
from  water  which  had  presumably  been  the  cause  of  an  out- 
break of  the  disease.  In  the  outbreak  in  Providence  in  that 
year  Prudden  and  Ernst  reported  finding  the  bacilli  in  house 
filters.  Methods  of  identifying  the  bacillus  at  that  time  were, 
however,  not  entirely  satisfactory,  and  it  is  not  certain  that 
the  bacteria  isolated  were  really  typhoid  bacilli.  By  better 
methods  the  germs  have  since  been  occasionally  found  in 
infected  waters,^  but  as  might  be  expected,  it  is  more  often 
from  wells  than  from  rivers  or  lakes.  According  to  Got- 
schlich,^  typhoid-fever  germs  have  been  identified  in  drinking 
water  by  the  agglutination  test  only  four  times.  Since  then, 
however,  they  have  been  isolated  by  Wesbrook^  from  the 
Mississippi  water  at  Minneapolis,  and  by  Fox  from  the  reser- 
voir which  was  the  source  of  the  Scranton  outbreak.^  The 
bacillus  isolated  by  Wesbrook  was  used  for  years  as  a  test 
organism  in  his  laboratory  and  also  by  Harris  at  Johns  Hop- 
kins. Anderson  and  Hutchings  and  Wheeler,  as  will  be  re- 
ferred to,  determined  the  presence  of  typhoid  bacilli  in  ice 
presumed  to  be  the  cause  of  the  disease. 

1  Chapin,  Boston  M.  &  S.  J.,  1889,  CXX,  604. 

2  J.  Mass.  Ass.  Bds.  Health,  Bost.,  1904,  XIV,  66. 

*  Gotschlich,  Kolle  u.  Wassermann,  Handbuch  [etc.],  Jena,  1903, 
I,  191. 

*  Wesbrook,  Brit.  M.  J.,  1897,  II,  1774. 

»  Rep.  St.  Bd.  Health,  Penn.,  1907,  410.  ' 


270        THE  SOURCES  AND  MODES  OF  INFECTION 

Temporary  Typhoid  Infection.  —  These  explosive  and  tem- 
porary outbreaks  of  typhoid  fever  among  the  users  of  muni- 
cipal supplies  are  sometimes  due  to  an  accidental  pollution 
with  sewage,  but  are  more  often  due  to  the  overflow  of  privies, 
or  the  placing  of  the  discharges  of  typhoid  patients  on  the 
ground  where  they  can  be  washed  into  the  streams.  In  our 
lake  cities  they  have  sometimes  resulted  from  the  wind  tem- 
porarily blowing  the  sewage  of  the  city  towards  the  intake  of 
the  waterworks,  1  or  the  dumping  of  dredged  mud  near  the 
intake.^  Outbreaks  are  sometimes  due  to  the  careless  tem- 
porary use  of  polluted  water,  owing  to  failure  of  the  good 
supply,  as  at  Newburyport,^  or  the  accidental  sucking  in  of 
polluted  water  owing  to  some  derangement  of  valves  or  other 
mechanism,  as  in  Lowell,*  Baraboo  and  Millinocket.^ 

Continuous  Typhoid  Infection.  —  When  considerable 
amounts  of  sewage  are  discharged  into  a  stream  or  lake,  the 
water,  owing  to  the  prevalence  of  typhoid  fever,  must  be 
continuously  charged  with  the  bacilli.  The  users  of  the 
water  under  such  circumstances  generally  suffer  from  a  con- 
tinuously high  death  rate  from  this  disease.  Among  cities 
which  have  so  suffered  may  be  mentioned  Chicago,  Pitts- 
burg, Cincinnati,  St.  Louis,  Philadelphia,  Newark  and  Al- 
bany. The  unenviable  position  of  many  Pennsylvania  cities 
in  this  respect  is  well  set  forth  by  Morris.''  Among  Euro- 
pean cities  which  have  had  a  bad  water  supply  are  Berlin, 
Hamburg,  Paris,  Frankfurt,  Altona,  Breslau  and  Zurich. 
Under  these  circumstances  the  typhoid  rate  may,  while  re- 
maining high,  vary  considerably.  Sometimes  the  incidence 
of  the  disease  may  reach  enormous  proportions,  as  in  Chicago 

1  Whipple,  Typhoid  Fever,  New  York,  1908,  167-168. 

2  Whipple,  Typhoid  Fever,  New  York,  1908,  167;  also  U.  S.  Geol. 
Survey,  Wash.,  Water  Supply  and  Irrigation  Papers,  No.  194,  138. 

3  Rep.  St.  Bd.  Health,  Mass.,  1892,  701. 

*  Whipple,  Typhoid  Fever,  New  York,  1908,  174. 

*  Whipple,  Typhoid  Fever,  New  York,  1908,  178-179. 
°  Morris,  Sanitation,  Phila.,  August,  1904,  47. 


INFECTION  BY  FOOD  AND  DRINK  271 

in  1891,  when  it  was  173.8  per  100,000,  and  in  Pittsburg  in 
1900,  when  it  was  144.2.  Sometimes  epidemic  waves  of  the 
disease  can  be  followed  down  a  river  from  one  municipality 
to  another,  as  in  the  ]\Ierrimac,  Kennebec  and  Hudson.' 

Cities  with  Infected  Water.  —  The  connection  between  an 
excessive  typhoid  death  rate  and  the  sewage  contamination 
of  municipal  water  supplies  is  thus  shown  by  a  large  amount 
of  epidemiological  evidence,  but  it  is  even  more  certainly  dem- 
onstrated by  the  improvement  which  almost  alwaj-s  follows 
when  a  pure  water  is  substituted  for  the  impure.  Formerly 
typhoid  fever  was  very  common  in  English  cities,  but  now 
the  disease  is  far  less  prevalent,  due  in  large  measure  to  the 
almost  universal  use  of  clean  water.  Many  continental  cities 
present  marked  illustrations  of  the  decrease  in  typhoid  fever, 
due  to  improvement  in  water  supply.  Among  such  may  be 
mentioned  Paris,  Berlin,  Altona,  Hamburg,  Zurich,  Breslau 
and  Frankfurt.  The  United  States  also  presents  numerous 
examples,  as  Lawrence,  Lowell,  Alban}',  Buffalo,  Newark, 
Jersey  City,  Cleveland,  Chicago  and  Philadelphia.  (For  more 
detailed  information  see  Whipple,  "Typhoid  Fever;"  Fuertes, 
"Water  and  Public  Health;"  Hazen,  "The  Filtration  of  Public 
Water  Supplies;"  and  Hazen,  "Pure  Water  and  How  to  Get 
It.")  It  has  in  one  or  two  instances  happened  that  the  purifi- 
cation of  a  polluted  water  supply  has  not  resulted  in  any  very 
marked  diminution  in  the  typhoid  death  rate.  This  was  so 
at  Youngstown,  Ohio,  and  notably  at  Washington.-  At 
Youngstown  the  disease  was  shown  to  be  spread  chiefly  by 
contact,  or  by  the  use  of  infected  wells.  The  conditions  at 
Washington  are  not  so  well  understood,  and  a  special  com- 
mission ^  has  been  able  to  find  no  very  definite  cause  for 
the  disease.     Levy  and  Freeman*  after  a  very  careful  study 

'  Whipple,  Typhoid  Fever,  New  York,  1908,  149,  154,  236. 
2  Whipple,  Typhoid  Fever,  New  York,  1908,  248. 
»  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Hyg.  Lab.,  Bull.  Nos.  35, 
44  and  51. 

<  Levy  and  Freeman,  Old  Dominion  J.  M.  &  S.,  1908,  VII,  315. 


272        THE  SOURCES  AND  MODES  OF  INFECTION 

of  conditions  in  Washington  and  Richmond,  conclude  ihat 
Washington  must  be  put  in  the  category  of  southern  cities 
in  which  an  excessive  typhoid-fever  rate  depends  chiefly  on 
cHmatic  conditions  operating  more  or  less  directly,  and  that 
perhaps  to  a  considerable  extent  the  disease  depends  on  the 
presence  of  flies.  However  that  may  be,  Washington  affords 
a  practically  unique  example  among  large  cities  of  a  mistake 
in  attributing  the  excess  of  typhoid  fever  to  the  pollution  of 
the  water  supply. 

Amount  of  Sickness  Due  to  Water.  —  To  how  great  an 
extent  pollution  of  public  water  supplies  is  responsible  for  the 
excessive  typhoid  mortality  in  the  United  States  it  is  difficult 
to  determine.  Whipple'  says  that  the  average  typhoid  death 
rate  in  American  cities  is  about  35  per  100,000,  while  cities 
with  a  good  water  supply  average  not  over  20.  He  would 
thus  attribute  to  the  pollution  of  public  water  supplies  about 
40  per  cent  of  the  typhoid  fever  of  the  cities  of  the  United 
States.  We  must  remember,  however,  that  an  excess  of 
typhoid  fever  in  a  city  with  a  questionable  water  supply  is 
not  always  due  to  the  water,  as  witness  Washington  and 
Youngstown,  and  Dr.  H.  W.  Hill  writes  me  that  Duluth  is 
another  example.  But  a  majority  of  the  people  of  this  coun- 
try live  beyond  the  reach  of  municipal  water  supplies,  and 
typhoid  fever  is  even  more  prevalent  among  this  rural  popu- 
lation. So  that  if  the  whole  country  is  considered,  it  appears 
that  10  or  15  per  cent,  rather  than  40  per  cent,  of  our  typhoid 
fever  is  the  proper  proportion  to  attribute  to  the  infection  of 
municipal  supplies. 

Amount  Due  to  Wells.  —  Doubtless  the  majority  of  the 
inhabitants  of  the  United  States  obtain  their  drinking  water 
from  wells.  Formerly  polluted  wells  were  believed  to  be  the 
chief  source  of  typhoid  fever.  This  was  particularly  so  while 
Murchison's  "pythogenic"  theory  of  the  origin  of  the  disease 
prevailed.  When  wells  were  a  principal  source  of  supply  in 
cities  where  privy  vaults  and  cesspools  abounded,  probably 
1  Whipple,  Typhoid  Fever,  New  York,  1908,  132. 


INFECTION  BY  FOOD  AND  DRINK  273 

they  were  often  the  source  of  typhoid  fever.  With  the  sub- 
stitution of  municipal  pipe-supphes,  the  well  has  become  a 
factor  of  comparatively  little  moment  in  city  typhoid  fever. 
As  it  now  appears  that  the  bacillus  of  this  disease  does  not 
survive  long  in  soil  or  water,  and  that  each  case  must  have 
some  connection  with  a  previous  case  of  human  typhoid 
infection,  it  seems  improbable  that  country  wells,  largely  iso- 
lated as  they  must  be  from  danger  of  indiscriminate  human 
contamination,  play  an  important  part  in  the  propagation  of 
the  disease.  This  is  the  view  held  by  Hill,  who  has  had  a 
large  experience  in  the  study  of  this  disease  in  Minnesota. 
He  states,  however,  that  sometimes  in  loose  coarse  gravel, 
or  in  seamy  shale  and  limestone  formations,  wells  may  become 
infected  from  sources  of  pollution  situated  at  long  distances, 
and  have  then  been  known  to  be  the  cause  of  much  sickness. 
Instances  of  Infected  Wells.  —  That  wells  have  actually 
been  the  source  of  typhoid  fever  there  is  much  evidence. 
Instances  of  outbreaks  due  to  infected  wells  at  Basingstoke, 
England,  Newport,  R.  I.,  and  Trenton  are  narrated  by  Whip- 
ple,' and  a  dozen  or  more  instances  in  England  are  referred  to 
by  Poore,^  and  some  of  the  179  milk  outbreaks  of  typhoid 
fever  tabulated  in  "  Milk  and  Its  Relation  to  the  Public 
Health"^  were  due  to  infection  of  the  milk  by  water  from  a 
contaminated  well.  Outbreaks  due  to  well  water  continue 
to  be  reported  from  time  to  time.  During  twenty-five  years 
no  instance  of  typhoid  fever  from  infected  well  water  has 
come  under  my  personal  notice  except  at  a  summer  hotel  on 
the  shore  of  the  bay,  in  which  case  the  well  was  probably 
infected  by  a  broken  drainpipe  near  by.  An  interesting  case 
was  noted  in  Washington  a  few  years  since.'*  Typhoid  fever 
occurred  in  four  houses  on  a  certain  street,  all  supplied  from 

>  Whipple,  Typhoid  Fever,  Now  York,  1908,  183-188. 
2  Pooro,  The  Eurth  in  Relation  to  the  Preservation  and  Destruc- 
tion of  B:\fteria,  Lond.,  1902,  i;3.5. 

»  U.S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Hyg.  Lab.  Bull.  No.  41,  50. 
*  District  of  Columbia,  Report  of  Health  Officer,  1903,  29. 


274        THE  SOURCES  AND  MODES  OF  INFECTION 

wells.  A  little  further  up  the  street  there  had  previously 
been  some  cases,  the  feces  from  which  had  been  thrown  into 
a  privy  box  after  what  was  probably  only  partial  disinfection 
with  carbolic  acid.  At  any  rate  carbolic  acid  could  be  tasted 
in  the  water  in  the  wells  below.  While  in  this  instance  the 
infecting  material  probably  percolated  through  the  soil,  as 
it  did  also  in  the  outbreak  at  Trenton,  Whipple  states:' 
"  Sandy  soil  is  a  good  filtering  material,  and  when  a  well  in 
such  soil  stands  at  the  center  of  a  circle  twenty-five  or  fifty 
feet  in  radius  in  which  there  are  no  privies,  cesspools,  sink 
wastes,  or  other  sources  of  contamination,  the  water  can 
usually  be  depended  upon  as  fit  for  domestic  use, — provided, 
of  course,  that  the  top  of  the  well  is  properly  guarded  against 
surface  wash."  Sometimes,  as  in  the  Trenton  incident,  the 
infecting  material  passes  a  considerable  distance  apparently 
through  channels  or  crevices.  The  writer  once  knew  of  a  well 
which  became  polluted  (though  without  causing  sickness) 
from  a  privy  300  feet  distant,  after  there  had  been  much 
blasting  near  by,  which  presumably  opened  seams  in  the 
somewhat  slaty  rock.  As  Whipple  says,  most  wells  which 
have  been  the  cause  of  typhoid  outbreaks  have  been  contam- 
inated from  the  top. 

Infected  Springs.  —  Springs  are  essentially  natural  wells, 
and  there  is  no  reason  why  they  should  not  occasionally  be 
contaminated.  A  typhoid  outbreak  caused  by  spring  water 
occurred  at  Mount  Savage,  Md.,  in  1904,^  another  at  Spring- 
field, Mass.,^  one  at  Northampton,  Mass.,^  one  at  Ridgway, 
Penn.,^  and  two  others  in  Maryland.® 

T3rphoid  Fever  from  Bathing.  —  It  has  been  suggested 
from  time  to  time  that  typhoid  fever  may  result  from  bathing 

^  Whipple,  Typhoid  Fever,  New  York,  1908,  85. 

2  Whipple,  Typhoid  Fever,  New  York,  1908,  188. 

3  Rep.  Bd.  Health,  Springfield,  1903,  16. 

4  Rep.  St.  Bd.  Health,  Mass.,  1900,  844. 
6  Rep.  St.  Bd.  Health,  Penn.,  1907,  927. 

«  J.  Am.  M.  Ass.,  Chicago,  1905,  XLIV,  595. 


INFECTION  BY  FOOD  AND  DRINK  275 

in  water  containing  typhoid  bacilli,  the  infection  presumably 
being  due  to  the  accidental  swallowing  of  some  of  the  water. 
Reece  ^  has  recently  reported  an  outbreak,  presumably  due 
to  this  cause,  at  the  naval  recruiting  station  at  Walmer.  The 
swimming  tank  was  infected  with  sewage  containing  typhoid 
excreta,  and  the  earlier  cases  seemed  to  be  closely  connected 
with  the  use  of  the  tank.  From  the  report,  however,  it  does 
not  appear  that  contact  infection  outside  the  tank  could  be 
rigidly  excluded. 

Cholera  from  Water.  —  Cholera  was  early  showTi  to  be 
a  water-borne  disease.  The  longevity  of  the  spirillum  in 
water  is  probably  not  so  great  as  that  of  the  typhoid  bacillus, 
but  it  is  sufficient  to  permit  of  the  disease  being  easily  trans- 
mitted in  this  manner.  Whenever  the  excreta  of  human 
beings  infected  with  cholera  gain  access  to  cisterns,  wells, 
streams  or  other  sources  of  drinking  water,  cholera  is  pretty  sure 
to  follow.  The  cholera-infected  Broad  Street  well  in  London 
has  been  referred  to,  and  although  for  many  years  the  views 
of  health  officials  were  somewhat  colored  by  the  miasm  theory 
of  Pettenkofer,  the  transmission  of  the  disease  by  water  was 
kept  in  mind,  and  man}'  outbreaks  due  to  this  cause  were 
reported.  Radcliffe,  Simon  and  others  ^  showed  that  infected 
water  played  a  large  part  in  the  outbreaks  of  cholera  in  Lon- 
don in  1848-49,  1853-54  and  1866.  Shakespeare  in  his  very 
valuable  Report  on  Cholera  in  Europe  and  India ^  gives  nu- 
merous instances  of  water-borne  cholera  infection,  as  from 
wells  at  several  places  in  France  (pp.  76-81),  and  from  muni- 
cipal supplies  in  Genoa  and  Naples  (p.  151).  In  Spain  many 
towns  and  villages  suffered  from  water-borne  outbreaks, 
caused  often,  doubtless,  by  the  universal  custom  of  washing 
soiled  linen  in  running  streams.  According  to  Shakespeare, 
water  plays  an  important  part  in  the  spread  of  cholera  in 

»  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  1908-09,  XXXVIII,  90. 
*  Sedgwick,  Principles  of  Sanitary  Science  and  the  Public  Health, 
New  York,  1902,  182. 

»  U.  S.  Government  Printing  Office,  1890. 


276        THE  SOURCES  AND  MODES  OF  INFECTION 

India,  and  Koch^  reported  finding  the  spirilla  in  a  tank  used 
as  a  village  water  supply.  A  number  of  instances  of  the 
finding  of  cholera  spirilla  in  water  that  was  presumably  the 
cause  of  the  disease  are  noted  by  Kolle.^  Cases  are  recorded 
of  explosive  outbreaks  of  cholera  on  shipboard,  probably  due 
to  infected  water.^  The  most  striking  instance  of  the  trans- 
mission of  cholera  by  water  is  the  celebrated  outbreak  in 
Hamburg  and  Altona  in  1892.  These  two  municipalities 
form  practically  one  city,  though  each  has  its  own  water 
supply.  In  the  outbreak  Hamburg,  which  used  unfiltered 
and  polluted  Elbe  water,  suffered  severely,  while  Altona,  the 
water  for  which  was  filtered,  was  almost  exempt.  The  line  of 
demarcation  between  the  two  water  supplies  could  be  recog- 
nized by  the  incidence  of  the  disease.  Our  officers  in  the 
Philippines  attribute  great  importance  to  water  as  a  vehicle 
for  the  diffusion  of  cholera,  particularly  in  the  villages  and 
smaller  towns,  where  the  streams  are  used  for  washing  clothes 
and  for  sewers  and  at  the  same  time  as  sources  of  domestic 
supply.  The  municipal  supply  of  Manila  has  been  kept  free 
from  infection  during  the  last  outbreaks,  though  wells  have 
to  some  extent  been  the  cause  of  sickness.  Woodruff*  states 
that  in  one  town  a  spring  supplied  part  of  the  people,  who 
were  quite  free  from  the  disease,  which  nearly  decimated  those 
using  the  river,  and  in  those  towns  where  the  people  had  well- 
protected  rain-water  cisterns  they  were  quite  immune.  While 
we  are  not  in  a  position  to  determine  the  relative  importance 
of  water  in  the  causation  of  cholera,  it  appears  certain  that  it 
is  a  factor  of  great  consequence,  and  that  people  using  a 
sewage-polluted  water  are,  on  the  advent  of  cholera,  liable  to 
suffer  from  severe  epidemics  of  the  disease. 

Dysentery  from  Water. — The  bacillus  of  dysentery  is  found 
in  the  discharges  from  the  bowels,  and  has  about  the  same 

1  Koch,  Brit.  M.  J.,  Lond.,  1884,  II,  403,  453. 

*  Kolle  u,  Wassermann,  Handbuch  [etc.],  Jena,  I,  191;  III,  61. 
3  Wendt,  Asiatic  Cholera,  New  York,  1885,  113. 

*  Woodruff,  J.  Am.  M.  Ass.,  1905,  XLV,  1160. 


INFECTION  BY  FOOD  AND   DRINK  211 

resistance  as  the  typhoid  bacillus,  so  that  we  should  expect 
this  form  of  dysentery  to  spread  in  much  the  same  way  as 
typhoid  fever  does,  and  that  infected  water  would  prove  a 
factor  of  importance.  Shiga  ^  reports  outbreaks  in  Japan  from 
the  use  of  well  and  river  water.  Eldridge^  states  that  dysen- 
tery is  a  rural  disease  in  Japan,  and  the  use  of  human  feces 
as  a  fertilizer,  and  the  frequency  of  the  infection  of  the  nu- 
merous small  streams  and  wells,  renders  it  preeminently  a 
water-borne  disease. 

The  causative  agent  of  amebic  dj'sentery,  according  to 
Musgrave  and  Clegg,  grows  outside  of  the  body  in  soil  and 
on  various  vegetables.  It  is  therefore  likely  to  be  trans- 
mitted by  water,  and  indeed  was  recovered  by  Musgrave  and 
Clegg  ^  from  17  of  61  samples  of  the  pubUc  water  supply  of 
Manila,  and  was  found  in  tanks  used  for  holding  distilled 
water,  and  also  in  many  wells.  Recently  Allan^  has  re- 
ported a  small  outbreak  of  amebic  dysentery  in  North  Caro- 
lina, due  to  an  infected  well. 

Diarrhea  from  Water. — Diarrhea  has  been  thought  by  some 
to  be  due  to  the  infection  of  drinking  water.  Thus  Reincke^ 
states  that  infantile  diarrhea  was  greatly  lessened  after  the 
improvement  in  the  water  supply  of  Hamburg.  Sir  Shirley 
F.  Murphy,  Seaton  and  Newsholme  in  the  discussion  of  the 
paper  took  issue  wdth  its  writer  as  to  the  part  played  by 
water  in  the  causation  of  this  disease.  Sedgwick^  says  that 
there  is  no  doubt  that  drinking  water  is  the  ready  vehicle  of 
dysentery  and  diarrhea.  He  refers  to  the  Ninth  Report  of 
the  Medical  Officer  of  the  Privy  Council,  London,  1867,  p.  16, 

1  Shiga,  Mod.  Med.  [Osier],  Phila.  &  N.  Y.,  1907,  II,  781. 

2  p:idridgc,  U.  S.  Pub.  Health  &  Mar.  Hosp.  Sorv.,  Pub.  Health 
Rep.,  1900,  1. 

'  Mu-sgrave  and  Clegg,  Bull.  18  Bu.  Gov.  Lab.,  P.  I.,  93;  Rep.  Bd. 
Health,  P.  I.,  1904-05,  10. 

*  Allan,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  1561. 

5  Reinckc,  Trans.  Epidemiol.  Soc,  Lond.,  1904,  n.  s.,  XXIII,  135. 

«  Sedgwick,  Principles  of  Sanitary  Science  and  the  Public  Health, 
New  York,  1002,  217. 


278        THE  SOURCES  AND  MODES  OF  INFECTION 

and  to  his  own  investigations  as  to  the  excessive  prevalence  of 
typhoid  fever  and  diarrhea  in  Burhngton  owing  to  the  sewage 
contamination  of  the  water  supply.^  In  Albany  ^  there  was 
a  reduction  of  57  per  cent  in  the  mortality  from  diarrheal 
diseases  after  the  introduction  of  filtration  in  1898.  Such 
statistical  evidence  does  not  seem  to  the  writer  to  be  of  much 
value,  and  the  evidence  elsewhere  given  of  the  part  plaj^ed  by 
milk  and  contact  indicates  that  it  is  improbable  that  water 
has  much  influence  in  the  causation  of  diarrheal  diseases. 

Malaria  from  Water.  —  Until  recently  malaria  has  been 
believed  to  be  transmitted  by  means  of  drinking  water. 
Numerous  instances  were  reported,  such  as  that  of  the  ship 
Argo,  in  which  it  was  supposed  that  the  evidence  pointed 
conclusively  to  this  mode  of  transmission.  The  discovery  of 
the  part  played  by  the  mosquito  in  the  causation  of  this 
disease  led  to  a  more  critical  consideration  of  the  alleged 
evidence  in  support  of  its  water-borne  character,  and  most 
of  this  evidence  was  found  to  be  worthless,  or  in  the  few 
instances  in  which  water  still  seemed  to  be  at  fault  it  appeared 
probable  that  the  water  served  as  a  breeding  place  for  mosqui- 
toes, and  did  not  directly  cause  disease  by  its  ingestion. 

There  was  nothing  in  the  earlier  demonstrated  facts  of  the 
transmission  of  the  disease  by  insects  to  preclude  the  pos- 
sibility of  its  transmission  by  water,  and  indeed  Laveran  and 
Manson  thought  this  not  improbable.  Celli  ^  attempted  to 
demonstrate  this  in  various  ways  by  administering  water 
from  the  most  malarious  regions  of  Italy  to  human  beings, 
daily,  up  to  a  month.  He  failed  completely,  as,  according  to 
Craig,^  have  all  other  experimenters,  except  Ross  in  one  in- 
stance, which,  however,  from  the  conditions  of  the  experiment 
was  far  from  conclusive.  Celli  considers  the  fact  that  large 
numbers  of  railway  employees  and  others  living  in  intensely 

1  J.  N.  Eng.  Water  Works  Ass.,  X,  167. 

2  Whipple,  Typhoid  Fever,  New  York,  1908,  276. 
»  Celli,  Malaria,  Lond.,  1900,  94. 

<  Craig,  The  Malarial  Fevers,  New  York,  1909,  82. 


INFECTION   BY   FOOD   AND   DRINK  279 

malarious  regions  around  Rome  use  an  unquestionably  pure 
aqueduct  water,  but  are  yet  frequently  attacked  by  malaria, 
is  corroborative  evidence  that  water  cannot  be  an  important 
vehicle  of  the  disease.  But  probably  the  best  evidence  we 
have  that  drinking  water  plays  no  part  in  the  causation  of 
malaria  is  the  fact  that  preventive  measures  all  over  the 
world,  directed  solely  against  the  mosquito  and  with  no  ref- 
erence to  the  water  theory,  have  resulted  in  an  enormous  de- 
crease and  in  some  places  in  the  eradication  of  the  disease. 

Yellow  Fever  from  Water.  —  Yellow  fever  also  was  formerly 
beheved  to  be  at  times  water-borne,  but  as  in  malaria  the 
epidemiological  evidence  therefor  will  not  stand  criticism. 
The  success  of  the  preventive  measures  directed  solely 
against  the  mosquito  indicates  that  drinking  water  has  no 
part  in  the  diffusion  of  this  disease. 

Tuberculosis  from  Water.  —  Dixon  and  Fox^  showed  that 
tubercle  bacilli  may  be  recovered  from  sewage,  as  might  have 
been  suspected  from  what  is  known  of  the  biology  of  the  or- 
ganism. It  must  be  frequentl}'  swallowed  by  human  beings, 
and,  as  in  cattle,  is  likely  to  be  voided  in  a  living  state  in  the 
feces.  The  washings  of  pastures  and  stables  must  also  carry 
the  bovine  form  of  the  bacillus  in  considerable  numbers  into 
w^aters  jvhich  are  quite  free  from  pollution  by  human  excreta. 

Hazen  has  attempted  to  show  that  the  purification  of 
sewage-contaminated  public  water  supplies  decrea.ses  the 
general  death  rate  of  a  city,  as  well  as  the  typhoid  mortality. 
Thus  it  was  stated  that  the  use  of  filters  on  the  Albany  water 
supply  caused  a  decrease  in  deaths  from  malaria,  diarrheal 
diseases  and  also  a  general  decrease  in  the  deaths  of  children 
under  five  years  of  age.  During  a  study  of  this  claim  of 
Hazen's,  that  the  purification  of  a  polluted  water  supply 
results  in  a  marked  decrease  in  the  general  mortality,  Sedg- 
wick and  MacNutt^  came  to  the  conclusion  that  among  the 
diseases  thus  affected  pulmonary  tuberculosis  holds  an  im- 

»  Dixon  and  Fox,  J.  Am.  M.  Ass.,  Chicago,  1908,  LI,  380. 

2  Sedgwick  and  MacNutt,  Science,  N.  Y.,  1908,  n.  s.,  XXVIII,  215. 


280        THE  SOURCES  AND   MODES  OF  INFECTION 

portant  place.  These  writers  compared  the  phthisis  death 
curve  in  Lowell  and  Lawrence,  two  cities  which  some  years 
since  substituted  pure  for  impure  water,  with  the  curve  for 
the  same  disease  in  Manchester,  another  and  near-by  city 
with  a  similar  population  and  business,  which  for  a  long 
time  had  had  a  pure  and  unchanged  public  water  supply. 
During  the  five-year  periods  considered  the  phthisis  death 
rate  in  Lowell  fell  83  per  100,000  living,  and  in  Lawrence  59, 
while  Manchester  showed  a  decrease  of  onl}^  5  and  30  for  the 
same  periods.  (The  improvement  in  the  water  supply  of  Lowell 
and  of  Lawrence  was  not  made  at  the  same  time.)  The  total 
death  rate,  and  particularly  the  death  rate  from  pulmonary 
tuberculosis,  has  been  falling  very  generally  of  late,  and  the 
gross  death  rate,  and  even  that  for  a  single  disease  like  tuber- 
culosis, is  determined  by  a  very  large  number  of  factors.  To 
draw  such  far-reaching  conclusions  from  a  study  of  only  three 
cities  seems  somewhat  dangerous,  and  I  would  much  prefer 
to  consider  the  question  still  open  as  to  whether  the  incidence 
of  pulmonary  tuberculosis  is  affected  by  the  water  supply. 
The  above-named  writers  come  to  no  conclusion  as  to  whether 
the  decrease  in  the  death  rate  from  tuberculosis  is  due  to 
decrease  in  infection  or  improvement  in  resistance.  Sedg- 
wick and  MacNutt  also  believe  that  the  death  rate  from 
pneumonia  is  affected  by  the  water  supply. 

Worms  in  Water.  —  The  eggs  and  young  of  some  of  the 
parasitic  worms  are  often  swallowed  in  drinking  water,  and 
the  Ankylostoma  and  Bilharzia,  and  others  probably,  enter 
the  skin  from  water  in  which  they  are  contained,  but  the 
consideration  of  the  diseases  caused  by  them  is  outside  the 
scope  of  this  essay. 

Conclusions.  —  Among  the  common  infectious  diseases, 
typhoid  fever  is  practically  the  only  one  at  present  of  any  great 
importance  to  the  people  of  Western  Europe  and  North 
America  which  is  often  disseminated  by  means  of  drinking 
water.  It  is  probably  true  that  dysentery  also  may  be  spread 
in  the  same  way,  but  it  does  not  at  present  appear  to  be  very 


INFECTION   BY  FOOD  AND   DRINK  281 

common,  or  to  occur  often  in  water-borne  outbreaks.  Asiatic 
cholera  too  may  cause  great  devastation  through  infection  of 
water  supplies,  but  for  a  number  of  years  the  western  world 
has  been  remarkably  free  from  this  disease.  Typhoid  fever 
is,  however,  such  a  common  and  serious  disease,  causing  prob- 
ably 25,000  deaths  annually  in  the  United  States,  as  well  as 
an  enormous  amount  of  disability  at  the  most  useful  period 
of  life,  that  it  is  worth  while  to  make  large  expenditures  for 
its  prevention.  Such  expenditures  are  to  be  still  further 
encouraged,  since  it  is  certain  that  the  means  taken  to  pre- 
vent the  diffusion  of  typhoid  fever  by  water  will  also  prevent 
the  spread  of  cholera  and  bacillary  dysentery. 

Protection  of  Water  Supplies.  —  In  the  three  diseases  just 
mentioned  the  sole  source  of  infection  of  water  is  the  excreta 
of  persons  infected  with  the  specific  germs.  If  these  excreta 
can  be  kept  out  of  drinking  water,  or  if  the  germs  can  be 
removed  from  it  after  it  is  infected,  the  problem  is  solved,  and 
this  can  be  done  at  a  not  prohibitive  expense.  For  a  full 
and  practical  consideration  of  the  means  for  obtaining  a  pure 
water  supply  reference  should  be  had  to  such  works  as  Hazen's 
"The  Filtration  of  Public  Water  Supplies"  and  "Pure  Water 
and  How  to  Get  It."  Suffice  it  to  say  here  that  pure  water 
may  be  obtained  by  securing  a  clean  source  or  by  adopting 
some  method  of  purification. 

Domestic  Wells.  —  The  larger  part  of  our  population  ob- 
tains its  drinking  water  from  shallow  wells,  and  it  is  usually 
neither  difficult  nor  expensive  so  to  locate  them  that  they 
will  not  receive  drainage  from  privies  or  sink  drains,  and  so 
to  protect  them  that  they  will  not  receive  surface  washings. 
The  federal  Department  of  Agriculture  and  the  state  and  local 
boards  of  health  should  do  and  are  doing  much  to  instruct 
farmers  and  villagers  concerning  the  location  and  protection 
of  wells. 

Municipal  Supplies.  —  As  regards  municipal  supplies  it  is 
desirable  if  possible  that  the  water  be  uncontaminated.  This 
may  be  secured  by  drawing  from  deep  wells,  or  seeking  a 


282        THE  SOURCES  AND  MODES  OF  INFECTION 

source  in  a  sparsely  inhabited  region.  Some  cities,  as  Liver- 
pool, Boston  and  New  York,  have  spent  large  sums  to  bring 
clean  water  from  long  distances.  Other  cities,  notably  Chi- 
cago, have  secured  good  water  by  the  construction  of  expen- 
sive works  to  remove  sewage  from  the  watershed.  Many 
cities,  when  there  is  only  a  limited  danger  of  pollution,  ac- 
complish much  by  a  continuous  patrol  of  the  watershed 
and  the  removal  of  minor  sources  of  pollution  under  general 
or  special  nuisance  laws.  In  many  states  this  duty  of  pro- 
tection has  been  laid  upon  the  state  boards  of  health,  and 
in  some  instances  cooperation  between  states  becomes 
necessary. 

Purification  of  Water.  —  Unfortunately  it  often  happens 
that  it  is  physically  impossible  for  a  municipality  to  obtain 
a  sufficient  supply  of  water  which  is  not  subject  to  dangerous 
pollution.  Purification  then  becomes  a  necessity,  and  owing 
to  the  labors  of  a  long  line  of  chemists,  engineers  and  bacteri- 
ologists, several  efficient  and  economical  methods  for  accom- 
plishing this  have  been  developed.  First  among  these  is 
filtration.  There  are  various  methods  of  filtration,  applica- 
ble to  different  waters  and  different  localities,  and  it  is  the 
business  of  specialists  to  devise  the  best  system  for  each  city 
confronted  by  the  problem.  Efficient  filtration  will  remove 
over  99  percent  of  the  contained  bacteria,  but  cannot  be  relied 
upon  to  remove  amebse.  Hence  filtration  will  not  protect 
against  amebic  dysentery,  but  it  will  protect  against  the 
bacillary  form  and  against  typhoid  fever  and  cholera.  That 
it  is  efficient  against  typhoid  fever  is  shown  by  the  experience 
of  London,  Berlin,  Zurich,  Hamburg,  Lawrence,  Albany, 
Paterson,  Philadelphia  and  many  other  cities,  and  the  re- 
moval of  cholera  spirilla  was  beautifully  shown  by  the  ex- 
perience of  Altona  in  1893.  The  storage  of  water  rapidly 
removes  bacteria  by  sedimentation  and  through  the  death  of 
the  organisms,  and  is  often  a  useful  adjunct  to  filtration, 
notably  so  in  the  case  of  some  of  the  London  water  companies. 
The  boiling  of  water  is  an  effectual  means  of  destroying  dan- 


INFECTION  BY  FOOD  AND  DRINK  283 

gerous  bacteria,  and  as  a  domestic  measure  it  is  sometimes 
extremely  useful. 

The  use  of  hypochlorite  of  lime  (commercial  bleaching 
powder)  has  within  a  short  time  come  into  use  for  the  pur- 
pose of  sterilizing  municipal  water  supplies.  Wliile  this 
method  of  protection  had  been  used  in  England  as  a  tem- 
porary expedient,  its  first  use  as  a  permanent  method  of 
treatment  seems  to  have  been  by  Leal,  at  Boonton,  N.  J., 
in  1908.^  A  high  degree  of  safety  seems  to  be  secured  at  a 
low  cost.  The  subject  has  been  investigated  also  by  Clark 
and  Gage,"  Phelps,  Park,  Pratt  and  others.  The  process  has 
been  used  at  East  Providence,  R.  I.,  Poughkeepsie,  Chicago 
and  other  places.^ 

Infection  by  Ice. 

Danger  Exaggerated.  —  The  use  of  ice  from  polluted 
sources  has  always  been  viewed  with  some  alarm,  and  when 
it  became  known  from  the  work  of  Prudden^  and  others  that 
the  bacilli  of  typhoid  fever  live  for  some  months  when  frozen 
into  ice,  the  alarm  was  believed  to  be  well  founded.  But 
further  researches  (see  page  10)  have  shown  that  in  the 
freezing  of  ice  under  normal  conditions  a  large  proportion 
of  the  bacteria  in  the  ice  are  frozen  out,  and  those  that  remain 
tend  to  die  off  quite  rapidly,  somewhat  as  they  do  in  water. 
Hence  theoreticall}'  little  danger  is  to  be  apprehended  from 
the  use  of  ice  cut  from  water  considerably  polluted,  even 
so  polluted  that  if  the  water  itself  were  used  it  would 
probably  cause  disease.  There  is  very  little  epidemiological 
evidence  that  ice  has  been  the  cause  of  sickness.  The  litera- 
ture relating  to  the  subject  was  collected  by  Sedgwick  and 

^  Leal,  Fuller,  Johnson,  Papers  read  at  the  29th  Annual  Con- 
vention of  the  American  Water  Works  Association,  1909. 

2  J.  N.  Eng.  Water  Works  Ass.,  1909,  XXII,  302. 

'  Di.scussion  of  a  paper  by  Phelp.s  at  a  recent  meeting  of  the  Boston 
Society  of  Civil  Engineers,  Abst.  Eng.  Rec,  1910,  XLI,  80. 

*  Prudden,  Med.  Rec,  N.  Y.,  1887,  XXXI,  341. 


284       THE  SOURCES  AND  MODES  OF   INFECTION 

Winslow  ^  in  1902.  An  outbreak  the  exact  nature  of  which 
was  not  determined  occurred  at  Rye  Beach,  N.  H.,  in  1875, 
due  presumably  to  the  use  of  ice  from  a  pond  grossly  polluted 
with  decaying  vegetable  matter.  A  single  case  of  typhoid  fever 
in  Connecticut  appeared  to  be  due  to  the  use  of  specifically 
infected  ice.  Alleged  outbreaks  of  typhoid  fever  and  dysen- 
tery in  the  United  States,  and  of  typhoid  fever  in  Evesham, 
England,  and  Rennes,  France,  were  also  noted  by  the  above- 
named  authors,  but  the  evidence  was  far  from  conclusive. 
More  recently  Hutchings  and  Wheeler  ^  report  an  outbreak 
of  typhoid  fever  in  a  hospital  at  Ogdensburg,  N.  Y.  Eight 
persons  were  attacked,  and  the  disease  seemed  to  be  due  to 
the  use  of  ice.  An  examination  of  the  ice  in  the  ice  house 
showed  that  some  of  it  contained  visible  dirt  from  which 
colon  and  typhoid  bacilli  were  isolated.  Anderson  ^  reports 
an  outbreak  at  Lexington,  Va.,  possibly  due  to  artificial  ice 
made  from  spring  water  polluted  with  typhoid  excreta,  from 
which  water  he  isolated  typhoid  bacilli,  proved  to  be  such 
by  cultural  and  agglutination  tests.  Hamer  *  refers  to  a  pos- 
sible instance  of  ice-borne  typhoid  in  London  in  1898.  Judg- 
ing from  the  small  number  and  indefinite  character  of  these 
reports,  it  appears  that  there  is  little  direct  evidence  that  ice 
is  a  factor  of  any  moment  in  the  diffusion  of  the  contagious 
diseases.  On  the  other  hand  there  is  strong  epidemiological 
evidence  that  it  is  not,  and  this  is  in  accord  with  the  bac- 
teriological findings.  Hundreds  of  thousands  of  tons  of  ice 
are  cut  from  sewage-polluted  waters  in  the  United  States, 
but  sickness  does  not  appear  to  follow  the  use  of  this  ice  in 
drinking  water.  Park^  has  studied  this  point  in  New  York 
City,  where  four-fifths  of  the  ice  is  cut  from  the  markedly 

1  Sedgwick  and  Winslow,  Mem.  Am.  Acad.  Arts  &  Sc,   1902,  XII, 
No.  5,  472. 

2  Hutchings  and  Wheeler,  Am.  J.  M.  Sc,  Phila.,  1^03,  n.  s.,  CXXVI, 
680. 

3  Anderson,  Med.  Rec,  N.  Y.,  1908,  LXXIV,  909. 

*  Hamer,  Rep.  Med.  Off.  Health,  Lond.,  1904,  Appendix  I. 
6  Park,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  731. 


INFECTION  BY  FOOD  AND  DRINK  285 

contaminated  Hudson  River.  Vast  quantities  of  this  ice  are 
used  in  drinking  water,  and  if  it  is  the  bearer  of  typhoid 
fever  there  should  begin  a  noticeable  increase  of  the  disease 
when  the  use  of  the  new  ice  commences  in  March,  and  this 
increase  should  continue  during  April  and  May.  During  the 
ten  years  studied  by  Park  no  such  increase  was  noted  -id 
no  outbreak  occurred  which  could  be  attributed  to  ice. 

Infection  by  Milk. 

Character  of  Outbreaks.  —  It  has  long  been  known  that 
some  of  the  common  contagious  diseases  of  human  beings 
may  be  transmitted  by  means  of  milk.  The  only  diseases 
that  are  definitely  known  to  be  so  carried  are  typhoid  fever, 
scarlet  fever  and  diphtheria.  There  is  no  reason  why  dysen- 
tery and  cholera,  and  perhaps  other  diseases,  should  not  be 
transmitted  in  the  same  way,  but  no  evidence  of  it  has  come 
to  my  knowledge,  except  that  referred  to  by  Kober,i  who 
states  that  McNamara  in  Calcutta,  in  1872,  traced  an  out- 
break of  cholera  to  an  infected  dairy.  Outbreaks  of  the 
above  diseases  have  been  reported  from  time  to  time,  and 
have  been  studied  by  Hart,  Kober  and  others,  but  the  latest 
tabulation  and  the  fullest  consideration  of  the  subject  are 
to  be  found  in  Bulletin  56,  Hygienic  Laboratory,  United 
States  Public  Health  and  Marine  Hospital  Service,  1909. 
Milk  outbreaks  of  these  diseases  have  an  explosive  character, 
such  as  is  shown  by  water-borne  outbreaks  of  typhoid  fever. 
In  scarlet  fever  and  diphtheria  the  explosive  character  is  owing 
to  the  shorter  incubation  of  these  diseases,  more  pronounced 
than  it  is  in  typhoid  fever.  A  milk  outbreak  is  determined 
to  be  such  from  the  presence  of  an  excessive  number  of  cases 
on  a  particular  milk  supply  which  cannot  be  accounted  for 
in  any  other  way.  From  three  to  five  cases  within  a  few 
days  on  a  route  covered  by  one  wagon  in  a  city  with  an 
average  typhoid  death  rate  is  highly  suspicious,  and  in  most 

•  Kober,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLIX,  1091. 


286       THE  SOURCES  AND  MODES  OF  INFECTION 

instances  proves  to  be  the  beginning  of  an  outbreak.  The 
more  the  customers  of  a  dealer  are  scattered,  the  stronger 
is  the  evidence.  Care  must  be  taken  to  exclude  all  other 
sources,  such  as  neighborhood  or  family  contact,  water,  ice, 
shellfish  or  other  foods.  Milk  outbreaks  often  prevail  more 
extensively  among  the  well-to-do,  owing  to  their  greater  con- 
sumption of  milk,  and  a  typhoid  milk  outbreak  usually  shows 
a  high  percentage  of  children  attacked.  Often  the  source  of 
infection  can  be  found.  In  only  two  instances  reported  by 
Konradi  ^  and  Shoemaker "  has  the  typhoid  bacillus  been 
isolated  from  milk,  and  in  only  four  instances  has  the 
diphtheria  bacillus  been  recovered.^ 

Number  of  Outbreaks.  —  The  number  of  outbreaks  pretty 
definitely  traced  to  milk  is  quite  large.  Trask,  in  the  Hygi- 
enic Laboratory  Bulletin  referred  to,  tabulated  179  outbreaks 
of  typhoid  fever,  51  of  scarlet  fever,  23  of  diphtheria  and 
7  of  sore  throat.  Besides  these  Hart  reported  51  of  typhoid 
fever,  and  Busey  and  Kober  86  of  typhoid  fever,  59  of  scarlet 
fever,  21  of  diphtheria,  making  in  all  316  outbreaks  of  typhoid 
fever,  125  of  scarlet  fever,  51  of  diphtheria  and  7  of  sore 
throat.  In  these  are  not  included  the  90  outbreaks  tabu- 
lated by  Caroe.  This  is  certainly  an  impressive  aggregate, 
but  it  must  be  remembered  that  these  records  cover  a  period 
of  perhaps  half  a  century.  To  determine  within  any  degree 
of  accuracy  how  large  a  part  milk  plays  in  the  spread  of 
these  diseases  is  difficult,  but  it  seems  to  me  that  the  tend- 
ency at  the  present  time  is  to  exaggerate  its  importance. 
Schiider  ^  found  that  of  640  outbreaks  of  typhoid  fever  462 
were  caused  by  water  and  110  by  milk,  but  it  is  highly  im- 
probable that  cases  caused  respectively  by  water  and  by  milk 

1  Konradi,  Centralbl.  f.  Bakteriol.  [etc.],  Jena,  I  Abt.  Orig.,  XL,  31. 

2  Shoemaker,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  1748. 

^  Nuttall  and  Graham-Smith,  The  Bacteriology  of  Diphtheria, 
Cambridge,  1908,  326. 

*  Schiider,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1901, 
XXXVIII,  343. 


INFECTION   BY  FOOD  AND  DRINK  287 

occur  in  any  such  ratio  in  the  United  States.  Most  of  the 
water-borne  typhoid  fever  does  not  occur  in  outbreaks,  but 
is  due  to  the  continuous  pollution  of  municipal  supplies. 
Milk-borne  typhoid  fever,  on  the  other  hand,  probably  does 
occur  chiefly  in  the  form  of  outbreaks.  During  the  last  four 
years,  in  Providence,  155  of  the  600  milk  dealers  have  had 
one  or  more  cases  of  typhoid  fever  on  their  routes.  In  only 
9  instances  have  there  been  more  than  2  cases  on  a  single 
route  within  a  week.  Investigation  promptly  showed  that 
in  3  instances  the  groups  of  cases  were  due  to  personal  con- 
tact, and  in  the  other  6  instances  an  unmistakable  milk 
outbreak  developed.  It  is  true  that  some  epidemiologists 
assume  that  a  considerable  number  of  sporadic  cases  are  due 
to  milk,  but  the  evidence  appears  to  be  the  other  way.  I 
think  that  a  study  of  the  distribution  of  typhoid  cases  on 
milk  routes  in  Washington,  as  shown  in  diagrams  in  bulletins 
35,  44  and  52  of  the  Hygienic  Laboratorj^,  United  States 
Public  Health  and  Marine  Hospital  Service,  bears  out  my 
contention  that  outbreaks  of  typhoid  fever  due  to  milk  are 
not  likely  to  escape  notice  if  the  cases  are  daily  tabulated 
according  to  milk  supply.  Furthermore,  these  charts  show 
that  there  is  little  excess  of  typhoid  fever  on  individual  milk 
supplies  except  in  those  instances  where  there  is  a  noticeable 
outbreak. 

Fewer  Outbreaks  in  Large  Cities.  —  It  is  also  to  be  noted 
that  very  few  outbreaks  are  reported  from  the  large  cities 
like  New  York,  Chicago  and  Philadelphia,  due  perhaps  to 
the  fact  that  the  chemical  and  bacteriological  changes  in  the 
milk  resulting  from  the  long  haul  necessary  for  such  cities 
are  unfavorable  for  the  typhoid  bacillus.  In  the  country, 
milk  outbreaks  are  not  likely  to  be  a  factor  of  moment,  as 
large  milk  routes  are  not  common.  It  is  in  the  medium-sized 
and  smaller  cities  and  villages  that  most  of  the  milk  out- 
breaks are  reported.  It  will  be  noted  that  though  scores  of 
outbreaks  of  typhoid  fever  may  occur  each  3'ear,  they  do  not 
include  more  than  a  small  fraction  of  the  total  typhoid  fever. 


288       THE  SOURCES  AND  MODES  OF  INFECTION 

It  may  be  claimed  that  only  a  small  proportion  of  the  milk- 
borne  outbreaks  are  recognized  as  such,  but  I  cannot  think 
that  this  is  so  in  the  English  cities  and  the  better  class  of 
American  cities.  In  Providence  during  the  last  twenty-five 
years  there  have  been  nine  outbreaks  of  typhoid  fever,  includ- 
ing 363  cases,  or  about  8  per  cent  of  the  total  occurring  during 
that  time.  But  the  typhoid  death  rate  in  Providence  is 
below  the  average,  so  that  8  per  cent  in  Providence  would 
probably  be  equivalent  to  not  over  4  per  cent  in  the  average 
American  city  with  its  polluted  water  supply  and  numerous 
privy  vaults.  In  only  a  few  cities  have  Trask,  Hart,  and  Busey 
and  Kober  been  able  to  find  records  of  more  than  two,  or  more 
rarely  three,  outbreaks;  yet  we  can  scarcely  believe  that  milk 
outbreaks  could  have,  except  rarely,  escaped  detection  in  the 
English  cities,  or  in  such  cities  as  Boston,  Worcester,  Spring- 
field, Rochester,  Baltimore,  Philadelphia  and  New  York. 

Amount  of  T3rphoid  Fever  Due  to  Milk.  —  The  city  of 
Washington  is  reported  as  showing  an  excessive  amount  of 
milk-borne  typhoid  fever.^  In  1906,  79,  or  9  per  cent,  of  the 
866  cases  investigated  by  the  commission,  were  traced  to  milk; 
in  1907,  31,  or  5  per  cent,  of  635  cases  investigated;  and  in 
1908,  54,  or  8  per  cent,  of  679  cases.  According  to  figures 
furnished  by  Dr.  Woodward,  Health  Officer  of  Washington, 
the  number  of  typhoid  cases  due  to  milk  during  the  three 
years  was  139,  which  gives  a  percentage  of  4.6.  The  com- 
mission considers  that  10  per  cent  of  the  typhoid  fever  in 
Washington  is  due  to  milk.  These  percentages, however, seem 
to  me  unfair,  as  doubtless  all  the  outbreaks  were  reported, 
and  the  percentages  should,  from  the  standpoint  of  the  present 
consideration,  be  based  on  the  total  number  of  cases  reported 
in  the  city,  and  not  on  the  cases  studied  and  of  known  origin. 
This  gives  a  percentage,  as  above  stated,  of  4.6  of  the  typhoid 
fever  in  Washington  during  the  three  years  1906-08  as  due 
to  milk-borne  typhoid.     The  importance  and  value  of  the 

1  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Hyg.  Lab.,  Bull.  No.  35, 
59;  No.  44,  46;  No.  52,  100. 


INFECTION  BY  FOOD  AND  DRINK  289 

reports  on  typhoid  fever  in  Washington  have,  as  it  appears, 
given  a  rather  exaggerated  importance  to  the  danger  from 
milk.  That  there  was  a  certain  amount  of  typhoid  fever  in 
Washington  due  to  milk,  during  the  three  years  in  question,  is 
no  reason  for  assuming  a  similar  percentage  of  milk-borne 
typhoid  fever  for  the  other  cities  of  the  country.  Trask  was 
able  to  find  during  the  years  1903-07  al)out  1900  cases  in 
the  United  States  traced  to  milk.  During  this  period  there 
were  in  the  registration  area  57,023  deaths,  and  the  total  num- 
ber in  the  whole  country  must  have  been  at  least  double,  or 
114,000.  The  fatality  is  probably  not  over  10  per  cent,  so 
that  there  must  have  been  at  least  1,000,000  cases.  Nine- 
teen hundred  is  0.19  per  cent,  which  is  very  different  from  the 
10  per  cent  now  commonly  assumed  as  due  to  milk.  I  do  not 
of  course  believe  that  all  the  milk  outbreaks  were  reported, 
but  the  number  would  have  to  be  increased  fifty-fold  to 
equal  10  per  cent,  and  it  can  scarcely  be  believed  that  98  per 
cent  of  all  milk  outbreaks  fail  of  recognition. 

Scarlet  Fever  and  Diphtheria.  —  Scarlet  fever  and  diph- 
theria are  certainly  much  more  rarely  transmitted  by  means 
of  milk  than  is  typhoid  fever.  Although  the  percentage  of 
typhoid  fever,  scarlet  fever  and  diphtheria  due  to  milk  is 
small,  the  danger  is  a  real  one  and  the  aggregate  of  cases  not 
inconsiderable,  and  their  occurrence  should,  if  possible,  be 
guarded  against. 

Animal  Sources.  —  The  infection  of  milk  with  the  above 
diseases  is  almost  invariably  from  human  sources.  There  is 
no  evidence  to  show  that  cows  may  be  infected  with  the 
bacillus  of  typhoid  fever,  and  the  contamination  of  the  milk 
by  drinking  sewage-polluted  water  does  not  occur.  Scarlet 
fever  also  does  not  appear  to  be  an  animal  disease.  Power 
and  Klein  in  England  believed  that  they  had  found  the  cause 
of  milk-borne  outbreaks  of  scarlet  fever  in  the  sickness  of  the 
cows  supplying  the  milk.  These  findings  have  not  been  sub- 
stantiated, and  the  micrococcus  which  Klein  believed  was 
the  cause  of  the  disease  has  not  been  accepted  as  such  by 


290       THE  SOURCES  AND  MODES  OF  INFECTION 

bacteriologists.  While  many  of  the  lower  animals  may  be 
successfully  inoculated  with  diphtheria,  the  disease  does  not 
appear  often  to  occur  spontaneously  among  them.  Never- 
theless two  milk-borne  outbreaks  have  been  traced  to  diph- 
theria of  the  cows'  udder.  One  of  these  was  reported  by  Dean 
and  Todd^  and  the  other  by  Ashby.^ 

Human  Sources.  —  Besides  the  bacteriological  evidence 
that  milk  rarely  acquires  its  infection  of  these  diseases  from 
animals,  we  have  the  direct  evidence  that  in  a  considerable 
number  of  outbreaks  the  milk  is  known  to  have  been  handled 
by  persons  sick  with  the  disease  or  carrying  its  organisms. 
-Trask  ^  says  that  in  113  of  the  179  outbreaks  of  typhoid  fever 
reported  by  him  an  infected  person  was  found  to  have 
handled  the  milk,  and  in  only  4  instances  was  the  infection 
reported  to  have  come  from  polluted  water  used  in  washing 
utensils,  and  in  4 others  to  the  use  of  milk  bottles  from  infected 
houses.  In  35  of  the  57  scarlet-fever  outbreaks  an  infected 
person  was  found  to  have  handled  the  milk,  and  3  others  were 
due  to  the  use  of  bottles  from  infected  houses.  Of  the  23 
diphtheria  outbreaks,  18  were  traced  to  handlers  of  the 
milk.  A  study  of  the  details  of  milk  outbreaks  shows  that  in  a 
large  proportion  the  infecting  case  was  not  recognized  as  such, 
that  the  symptoms  were  mild  or  atypical,  that  infection  oc- 
curred during  the  incipient  stage,  or  that  the  person  was 
merely  a  carrier.  Infection  may  occur  at  any  time  during  the 
handling  of  milk,  from  the  beginning  of  milking  until  the  milk 
is  delivered  to  the  consumer,  and  it  may  also  be  caused  by  those 
who  take  care  of  the  pails,  cans,  bottles,  strainers,  drums,  etc. 
Outbreaks  are  believed  to  have  been  caused  by  the  tasting  of 
milk  by  infected  dealers,  and  in  the  instance  reported  by 
Shoemaker  ^  a  convalescent  patient  was  in  the  habit  of  start- 

1  Dean  and  Todd,  J.  Hyg.,  Cambridge,  1902,  II,  194. 

2  Ashby,  Pub.  Health,  Lond.,  1906-07,  XIX,  145. 

3  Trask,  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Hyir.  Lab.,  Bull. 
No.  41,  25  et  .seq. 

4  Shoemaker,  J.  Am.  M.  Ass.,  Chicago,  1907,  LXVIII,  1748. 


INFECTION  BY  FOOD  AND   DRINK  291 

ing  a  siphon  from  the  milk  drum  by  sucking  the  tube.  It 
is  also  believed  by  many  that  flies  are  an  important  factor 
in  the  contamination  of  milk. 

Protection  of  Milk.  —  There  are  various  ways  in  which  the 
danger  from  infected  milk  may  be  avoided. 

First.  If  all  recognized  cases  of  the  diseases  just  considered 
are  promptl}^  reported,  and  proper  measures  of  isolation  are 
insisted  on,  there  will  be  a  considerable  decrease  in  the 
amount  of  milk-borne  infection.  When  such  a  disease  occurs 
in  the  family  of  a  milk  producer  or  dealer  the  patient  should 
usually  be  removed  from  the  premises,  and  the  vessels,  etc., 
if  possibly  infected,  should  be  disinfected.  The  greatest  diffi- 
culty is  encountered  in  the  management  of  convalescents, 
and  particularly  carriers,  and  it  is  the  view  of  most  health 
officers  that  the  latter  should  be  permanently  excluded  from 
the  milk  business.  Unfortunately  there  are  many  mild  cases 
of  contagious  disease  which  are  never  recognized  and  are  not 
likely  to  be.  Moreover,  persons  in  the  incipient  stage  are 
quite  likelj^  to  transmit  the  disease,  and  we  cannot  hope  for 
much  earlier  recognition  than  we  now  have.  Hence  for  the 
prevention  of  outbreaks  from  these  unknown  sources  we  must 
rely  on  other  methods. 

Second.  It  is  possible  to  reduce  the  chances  of  infection 
by  insisting  on  cleaner  methods  in  handling  milk  and  requir- 
ing the  sterilization  of  all  vessels,  particularly  of  bottles.  If 
all  handlers  would  wash  their  hands,  and  keep  their  hands 
out  of  the  milk  and  out  of  the  vessels,  there  would  be  no  milk 
outbreaks.  But  we  can  hope  for  no  very  radical  improvement 
as  regards  the  cleanliness  of  milkers,  farm  hands  and  peddlers. 

Third.  The  pasteurization  of  the  milk  by  the  dealer  before 
delivery  would  also  decrease  to  a  large  extent  the  amount  of 
milk-borne  disease,  for  a  study  of  outbreaks  shows  that  in  a 
large  proportion  the  infection  of  the  milk  takes  place  on  the 
farm.  But  there  is  also  considerable  risk  of  contamination  in 
the  hands  of  the  dealer  after  pasteurization. 

Fourth.     Doubtless  the  most  successful  way  of  preventing 


292       THE  SOURCES  AND  MODES  OF  INFECTION 

milk-borne  disease  at  the  present  time  is  for  the  pubhc  to 
consume  no  milk  except  that  which  has  been  pasteurized  or 
scalded  in  the  house.  Many  object  to  the  trouble  and  do  not 
like  the  taste  of  heated  milk,  so  that  this  practice  is  not  likely 
to  become  universal.  Moreover  outbreaks  have  occurred,  as 
at  Bristol,^  where  milk  pasteurized  in  an  institution  has  been 
afterwards  infected  by  a  maid. 

It  therefore  seems  that  while  it  is  possible  materially  to 
lessen  by  the  above  methods  the  amount  of  milk-borne 
disease,  we  cannot  hope  at  present  entirely  to  do  away  with 
the  danger  of  milk-borne  outbreaks  of  the  diseases  we  have 
been  considering. 

Ice  Cream.  —  As  milk  is  so  frequently  the  bearer  of  disease, 
it  [is  not  surprising  that  outbreaks  have  at  times  been  at- 
tributed to  food  products  derived  from  milk.  Thus  Soper  ^ 
reported  an  outbreak  due  to  the  use  of  cream  on  breakfast 
food,  and  one  of  the  outbreaks  reported  by  Trask  was  due  to 
whipped  cream.  Sedgwick  and  Winslow  ^  collected  records 
of  four  outbreaks  of  typhoid  fever  due  to  the  use  of  ice  cream, 
and  another  has  been  reported  by  Barras.* 

Butter.  —  While  it  has  been  shown  that  typhoid  bacilli 
may  live  for  some  time  in  butter,  no  outbreaks  seem  to  have 
been  reported  as  arising  from  the  use  of  this  substance.  This 
is  probably  due  partly  to  the  fact  that  the  germs  must  die 
off  pretty  rapidly,  leaving  perhaps  only  a  few  survivors,  and 
partly  to  the  difficulty  of  tracing  an  outbreak  to  such  a 
source. 

Views  concerning  Tuberculosis.  —  Of  all  the  animal 
diseases  which  are  transmissible  to  man  tuberculosis  has 
received  the  most  attention.     After  many  years  of  discussion 

1  Davies  and  Walker,  Proc.  Roy.  Soc.  Med.,  Lond.,  1908,  Epi- 
demiol. Sec,  175. 

2  Soper,  J.  Mass.  Ass.  Bds.  Health,  Bost.,  i904,  XIV,  68. 

3  Sedgwick  and  Winslow,  Mem.  Am.  Acad.  Arts  &  Sc,  1902,  XII, 
No.  5,  475. 

*  Barras,  Lancet,  Lond.,  1904,  II,  1281. 


INFECTION  BY  FOOD  AND  DRINK  293 

and  investigation  there  is  now  general  agreement  €hat  while 
the  two  types  of  tubercle  bacilli,  human  and  bovine,  are  dis- 
tinct and  cjuite  permanent,  they  are  reciprocally  infective, 
though  not  to  the  same  degree.  That  human  beings  may 
become  infected  with  tuberculosis  derived  from  cattle  is  now 
generally  admitted,  but  there  is  as  yet  no  general  agreement 
as  to  the  amount  of  such  infection,  though  present  views  are 
not  so  divergent  as  those  of  a  few  years  ago.  The  question 
of  the  mode  of  infection  in  tuberculosis  and  the  source  of  the 
bacilli  is  so  largely  dependent  on  pathological  evidence  that 
it  is  very  difficult  for  one  who  is  not  a  pathologist  properlj'  to 
weigh  the  evidence.  Yet  in  view  of  the  lack  of  agreement 
among  pathologists  it  becomes  necessary  for  the  health  officer, 
who  must  take  definite  action  to  com})at  the  disease,  to 
attempt  to  arrive  at  some  sort  of  conclusion.  It  seems  fair, 
from  the  evidence  thus  far  available,  to  draw  the  following 
conclusions: 

Bovine  Bacillus  may  infect  Man.  —  First.  The  bovine 
type  of  bacillus  is  capable  of  causing  infection  in  human 
beings.  This  is  shown  by  the  successful  inoculation  of  human 
beings  with  bovine  virus.  A  considerable  number  of  cases 
of  the  accidental  inoculation  of  veterinarians  and  laboratory 
workers  while  manipulating  animals  dead  with  tuberculosis 
have  been  reported  by  Pfeiffer,  Tscherning,  Xaughton,  Cop- 
pez,  Priester,  Hartzell,  Grothan,  Jadasohn,  Ravenel,  de 
Jong,^  Salmon "  and  others.  In  most  cases  the  lesion  was 
local,  and  some  have  argued  that  this  is  strong  evidence  of 
weakened  virulence  for  man.  The  finding  of  the  bovine  type 
of  the  bacillus  in  human  beings  is  generally  considered  as 
furnishing  a  more  certain  demonstration  of  the  latter's  suscep- 
tibility to  the  disease.  As  will  be  again  referred  to,  the  Ger- 
man and  British  commissions,  and  various  Americans,  have 

1  Mos.s,  Johns  Hopkins  Ho.sp.Rull.,  1909,  XX, 39; Cornet,  Xothnagel's 
Encyclopedia  of  Prartical  jMcdiciiie,  Phila.  &  Lond.,  1907,  Tubercu- 
losis, 77. 

»  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Bull.  Xo.  33,  16. 


294       THE  SOURCES  AA'D  MODES  OF  INFECTION 

found  the  bovine  bacillus  in  from  16  to  25  per  cent  of  the 
cases  studied.  These  facts,  while  demonstrating  the  suscep- 
tibility of  human  beings  to  the  bovine  form  of  the  disease, 
do  not  indicate  definitely  to  what  extent  the  bovine  type 
prevails  in  man,  as  the  cases  examined  were  usually  specially 
selected. 

Feeding  Experiments.  —  Second.  Tuberculosis  maj^  be 
produced  experimentally  in  animals  by  the  ingestion  of  mate- 
rial containing  tubercle  bacilli.  Milk  known  to  be  infected 
with  tubercle  bacilli  has  been  in  numerous  instances  fed  to 
guinea  pigs,  rabbits,  dogs,  calves,  swine  and  monkeys,  and 
has  caused  fatal  tuberculosis  in  them.  This  has  been  demon- 
strated by  a  large  number  of  workers  in  all  parts  of  the  world. 
A  good  summary  of  previous  experiments  is  given  by  Mohler,^ 
who  himself  produced  tuberculosis  by  feeding  guinea  pigs 
with  milk  from  tuberculous  cows.  Subsequent  experiments 
by  the  Bureau  of  Animal  Industry  ^  show  that  while  guinea 
pigs  are  with  difficulty  infected  by  feeding,  hogs  are  very 
easily  infected,  the  primary  infection  apparently  occurring  in 
the  submaxillary  glands,  the  lungs  usually  becoming  second- 
arily infected.^  That  the  ingestion  of  tuberculous  material, 
especially  milk  from  creameries,  is  the  chief  cause  of  tuber- 
culosis in  swine,  is  the  opinion  of  the  officers  of  this  depart- 
ment and  of  Ravenel  and  Russell.^  The  more  recent  work 
of  Calmette  and  the  French  school,  while  not  always  including 
direct  experiments  with  milk,  show  that  material  containing 
tubercle  bacilli,  introduced  in  any  way  into  the  stomach  or 
intestines,  results  in  the  production  of  tuberculosis,  and  even 
the  pupils  of  Fltigge  admit  that  the  ingestion  of  a  sufficient 
number  of  bacilli  will  cause  the  disease,  though  it  is  produced, 
they  say,  much  more  easily  by  inoculatipn  or  inhalation.     It 

,     1  Mohler,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Bull.  No.  44,  13. 

2  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Circ.  8-3,  Bull.  Nos.  S6,  8S,  93. 

3  Bull.  No.  88,  40*. 

*  Ravenel  and  Russell,  Am.  Pub.  Health  Ass.  Rep.,  1906,  XXXII, 
Pt.  I,  139. 


INFECTION  BY  FOOD  AND   DRINK  295 

is  also  generally  admitted  that  bacilli  may  be  absorbed 
through  the  intestines  without  leaving  any  lesion.  While 
some  pathologists  think  that  it  is  usually  possible  to  deter- 
mine the  route  of  infection  by  the  age  and  character  of  the 
lesions,  other  equally  good  men  do  not  consider  that  any  very 
reliable  conclusions  can  be  arrived  at  in  this  manner.  Under 
these  circumstances  it  appears  that  we  cannot  as  yet  appeal 
to  the  pathologists  for  a  definite  decision  as  to  the  mode  of 
infection  in  this  disease,  and  we  may  be  permitted  to  assume 
that  a  large  amount  of  tuberculosis  may  be  due  to  infection 
through  one  part  or  another  of  the  alimentary  canal. ^ 

Tubercle  Bacilli  in  Milk.  —  Third.  Tubercle  bacilli  are 
frequently  found  in  cows'  milk.  It  was  formerly  believed 
that  tubercle  bacilli  do  not  occur  in  cows'  milk  unless  the 
udder  is  diseased.  Nevertheless  various  observers  from  time 
to  time  have  reported  finding  the  bacilli  although  no  udder 
disease  was  evident.  Finally  Schroeder  and  Cotton"  showed 
that  frequently  the  feces  of  cattle  contain  large  numbers  of 
tubercle  bacilli,  although  the  animals  present  no  visible  symp- 
toms of  disease.  They  furthermore  showed  that  the  pollu- 
tion of  milk  with  infected  feces  is  the  most  common  source 
of  tubercle  bacilli  found  in  milk.  As  from  3  to  50  per  cent 
of  the  cattle  in  different  parts  of  the  United  States  react  to 
tuberculin,  and  probably  25  per  cent  of  the  cattle  in  Great 
Britain  are  infected,  it  is  not  surprising  that  market  milk  in 
these  countries  is  frequently  found  to  contain  tubercle  bacilli 
in  sufficient  numbers  to  cause  the  death  of  test  animals. 
Anderson  ^  gives  a  resum6  of  the  literature  of  the  subject. 
Among  the  percentages  of  infected  milk  referred  to  are,  in 
Copenhagen,  14.3  per  cent;  Boston,  21  per  cent  and  40  per  cent; 
Liverpool,  5.2  per  cent  from  city  dairies,  13.4  per  cent  from 

*  For  other  references  to  the  causation  of  tuberculosis  through  the 
alimentary  canal  see  p.  255. 

'  Schroeder  and  Cotton,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Bull.  No.  99. 

'  Anderson,  U.  S.  Pub.  Health  and  Mar.  Hosp.  Serv.,  Hyg.  Lab., 
Bull.  No.  41,  103. 


296       THE  SOURCES  AND  MODES  OF  INFECTION 

country  dairies,  though  later,^  owing  to  the  efforts  of  the 
authorities  in  eradicating  the  disease,  the  percentage  in  city 
dairies  was  1.4  per  cent  and  in  country  dairies  was  7  per  cent; 
Genoa,  9  per  cent;  London,  22  per  cent;  and  BerHn,  28  per 
cent.  Recently  of  620  samples  of  milk  consigned  to  London, 
61,  or  11.6  per  cent,  were  found  to  contain  tubercle  bacilli." 
Anderson  found  6.72  per  cent  of  223  samples  of  market  milk 
in  Washington  to  contain  virulent  tubercle  bacilli.  Hess  ^ 
found  virulent  tubercle  bacilli  in  16  per  cent  of  107  samples 
of  New  York  market  milk  (not  bottled).  He  thinks  the 
reason  that  his  percentages  are  higher  than  those  of  Anderson 
is  the  employment  of  more  test  animals  and  the  injection  of 
the  cream  as  well  as  the  milk.  He^also  found  virulent 
tubercle  bacilli  in  one  of  eight  samples  of  commercially  "  pas- 
teurized" milk.  In  Manchester,  England,  7.7  per  cent  of  542 
samples  of  milk  were  found  to  be  infected.* 

Danger  Less  than  Supposed.  —  There  seems  to  be  no 
doubt  that  a  large  part  of  the  milk  consumed  in  Europe  and 
the  United  States  contains  tubercle  bacilli  in  numbers  suffi- 
cient to  cause  the  disease  in  test  animals.  It  also  seems  to 
be  certain  that  in  the  lower  animals  at  least,  particularly  in 
young  individuals,  the  ingestion  of  this  tuberculous  milk  will 
cause  not  only  tuberculosis  of  the  aHmentary  canal,  but  will 
produce  pulmonary  disease  and  generalized  tuberculosis  also. 
It  is  probable  that  the  ingestion  of  such  milk  by  human  be- 
ings will  produce  similar  results.  There  is,  however,  consider- 
able variation  in  different  kinds  of  animals  as  regards  their 
susceptibility  to  this  sort  of  infection.  Even  in  animals  as 
susceptible  to  the  disease  as  are  guinea  pigs,  infection  by  the 
ingestion  of  milk  under  normal  conditions  is  not  very  easy. 
Thus  Schroeder  and  Cotton^  fed  132  guinea  pigs  with  tuber- 

1  Rep.  on  Health  of  Liverpool,  1906,  189. 

2  Rep.  Med.  Off.  Health,  Lond.,  1908,  60. 

»  Hess,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  IV,  523. 
*  Rep.  on  Health  of  Manchester,  1906,  187. 

^  Schroeder  and  Cotton,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Circ. 
No.  83. 


INFECTION  BY   FOOD   AND  DRINK  297 

culous  milk  on  the  average  for  forty-seven  days,  and  only  1, 
which  was  fed  for  357  days,  contracted  the  disease.  This 
was  onl}^  0.76  per  cent.  At  the  same  time  14.28  per  cent  of 
the  guinea  pigs  exposed  in  the  mangers  of  the  cows  from  which 
the  milk  was  obtained  developed  tuberculosis.  Dr.  Ver- 
ranus  Moore  writes  me  that  he  knows  of  a  small  village 
where  most  of  the  people  received  the  milk  from  a  herd 
of  cattle  that  later  was  found  to  be  extensively  diseased; 
that  is,  about  77  per  cent  reacted  to  tuberculin  and  some 
2  or  3  per  cent  showed  the  disease  on  physical  examination, 
and  a  considerable  percentage  of  the  guinea  pigs  inoculated 
with  the  mixed  milk  from  the  herd  died  of  tuberculosis. 
This  community  had  used  this  milk  for  a  number  of  years. 
After  the  facts  as  stated  alcove  were  ascertained  the  condi- 
tion was  changed  and  up  to  this  time  there  has  not  occurred 
a  single  case  of  recognized  tuberculosis.  Hess  '  examined  18 
children  who  a  year  previous  had  been  known  to  be  consum- 
ing tuberculous  milk.  None  of  them  showed  an}^  visible  signs 
of  tuberculosis,  though  4  reacted  to  the  tuberculin  test.  Of 
100  children  at  Randalls  Island,  N.  Y.,  fed  on  milk  from 
tuberculous  cows,  none  developed  the  disease."  A  recent 
note,^  which  I  have  not  had  the  opportunity  to  verify,  gives 
the  results  of  some  observations  made  by  Weber  of  the  Ger- 
man Imperial  Health  Office  on  the  use  of  tul^erculous  milk. 
From  Januarj'-,  1905,  to  April,  1908,  G9  cows  with  tuberculosis 
of  the  udder  were  kept  under  observation,  the  milk  from 
which  was  consumed  raw  by  360  persons,  of  whom  159 
were  children.  Of  these,  5,  of  whom  2  were  between  1 
and  2  years  of  age,  were  "  indubitably  infected  with  tuber- 
culosis through  the  use  of  the  milk."  The  children  had 
taken  the  milk  of  these  cows  from  one  to  one  and  a  half 
years.  In  both  cases  the  milk  was  used  raw  b}'  all  the  mem- 
bers of  the  family,  the  parents  and  several  children;  all  these 

1  Hess,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1014. 

2  Park,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  156. 
»  J.  Am.  M.  Ass.,  Chicago,  1910,  LIX,  886. 


298       THE  SOURCES  AND  MODES  OF  INFECTION 

people  remained  healthy.  In  the  sick  children  there  was 
merely  an  affection  of  the  cervical  glands  in  which  tubercle 
bacilli  of  the  typus  hovinus  were  demonstrated  by  bacteri- 
ological tests.  There  were  no  other  symptoms.  Whitla/ 
however,  reports  an  instance  where  of  150  children  fed  on 
milk  known  to  be  tuberculous,  15  contracted  the  disease. 

Percentage  Due  to  Bovine  Infection.  —  It  has  thus  far 
been  shown  merely  that  human  beings  7nay  contract  tuber- 
culosis by  drinking  the  milk  of  tuberculous  animals.  It  re- 
mains to  determine,  if  possible,  how  great  this  danger  really 
is.  Various  attempts  have  been  made  to  estimate  this.  It 
has  been  assumed  by  some  that  intestinal  tuberculosis,  and 
to  some  extent  generalized  tuberculosis  without  preponderant 
pulmonar}^  involvement,  is  indicative  of  infection  by  ingesta, 
and  presumably  by  milk.  The  fact  that  these  types  of  the 
disease  are  more  common  in  children,  of  whose  diet  milk 
forms  a  relatively  large  part,  has  been  thought  to  lend  color 
to  this  view.  It  is  not  improbable,  however,  that  the  dif- 
ferent form  which  the  disease  presents  in  early  life  may  be 
due  to  the  characteristics  of  the  age  rather  than  to  the  mode 
of  infection.  Children  certainly  consume  a  relatively  large 
amount  of  milk,  but  tuberculosis  is  not  so  common  among 
them  as  among  adults.  In  Providence  only  about  15  per  cent 
of  the  tuberculosis  is  in  children  under  five  years  of  age,  and 
only  about  4  per  cent  of  the  tuberculosis  death  rate  is  attrib- 
uted to  abdominal  tuberculosis.  In  the  registration  area  of 
the  United  States  abdominal  tuberculosis  accounts  for  about 
3.5  per  cent  of  all  deaths  from  this  disease.  This  form  of 
tuberculosis  appears  to  be  much  more  common  in  England.^ 
But  careful  observers  find  that  contact  with  other  cases  is 
probably  responsible  for  a  large  proportion  of  tuberculosis  in 
children.  Park  ^  states  that  of  100  cases  of  glandular  and 
bone  tuberculosis  in  St.  Mary's  Hospital,  New  York,  44  per 

'  Whitla,  Lancet,  Lond.,  1908,  II,  135. 

^  Bovaird,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  II,  446. 

3  Park,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  190S,  I,  157. 


INFECTION  BY  FOOD   AND   DRINK  299 

cent  had  been  in  close  contact  with  tuberculous  cases. 
LaFetra^  found  40.4  per  cent  of  131  cases  of  tuberculosis  in 
infants,  probably  due  to  family  infection.  Comby  '  considers 
family  infection  of  prime  importance  in  the  tuberculosis  of 
children.  Floyd  and  Bowditch  ^  found  that  679  of  1000 
tuberculous  children  had  been  in  contact  with  the  disease  in 
their  homes.  Approaching  the  subject  in  another  way,  they 
found  signs  of  the  disease  in  66  per  cent  of  746  children  living 
in  tuberculous  families  among  the  poor.  Miller  and  Wood- 
ruff* found  the  same  true  in  51  per  cent  of  150  children,  and 
Sacks  ^  in  5.3  per  cent  of  322  children. 

While  there  seems  to  be  no  doubt  that  tubercle  bacilli  iiiay 
remain  latent  in  the  body  for  some  time,  there  are  very  few 
who  accept  von  Behring's  view  that  most  human  tubercu- 
losis is  acquired  in  childhood  from  drinking  tuberculous  cows' 
milk.  As  greatly  discrediting  von  Behring's  theory  may  be 
mentioned  the  investigations  of  Speck,^  who  found  that  of 
8010  cases  of  tuberculosis  only  27  per  cent  had  been  fed  on 
cows'  milk  in  infancy.  Von  Ruck^  found  that  certainly  not 
over  25  per  cent,  and  possibly  not  over  10  per  cent,  had  been 
brought  up  on  cows'  milk.  Flick®  obtained  similar  evidence 
at  the  Phipps  Institute  in  Philadelphia.  Hej-mann®  says 
that  in  Christiania,  where  nearly  all  the  infants  are  nursed, 
tuberculosis  is  more  common  than  in  Bavaria,  where  artificial 
feeding  is  very  common,  and  that  in  Prague,  where  nearly  all 

'  LaFotra,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  II,  361. 

*  Comby,  Sixth  Intern.at.  Cong,  on  Tuberc,  Wa.sh.,  1908,  II,  503. 
»  Floyd  and  Bowditch,  Boston  M.  &  S.  J.,  1908,  CLIX,  783. 

*  Miller  and  Woodruff,  Sixth  Internat.  Cong,  on  Tuberc,  Wash., 
190S,  II,  487. 

*  Sacks,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  II,  479. 

«  Speck,  Ztschr.f.Hyg.u.Infoctionskrankh.,  Lpipz.,1904,  XLVIII,27. 
'  Von  Ruck,  J.  Am.  M.  Ass.,  Chicago,  190."),  XLIV,  1.3.50. 

*  Flick,  Report  of  Henry  Phipps  Inst.  Study  .  .  .  Tuberculosis, 
Phila.,  1906,  IV,  49. 

"  Heymann,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1904, 
XLVIII,  45. 


300       THE  SOURCES  AND   MODES  OF  INFECTION 

babies  are  breast  fed,  the  tuberculosis  death  rate  is  as  high 
as  in  any  city  in  Europe.  I  am  incHned  to  the  opinion  that 
such  epidemiological  facts  as  we  have  indicate  that  children 
are  more  susceptible  to  the  human  than  to  the  bovine  type 
of  the  disease,  and  there  seems  to  be  as  much  clinical  evidence 
that  the  tuberculosis  of  childhood  is  due  to  family  infection 
as  is  the  tuberculosis  of  adult  life. 

Instances  of  Milk  Infection.  —  Instances  are  not  rarely 
reported  in  which  there  is  considerable  evidence  of  the  pro- 
duction of  tuberculosis  in  children  by  the  use  of  milk  from 
tuberculous  animals.  One  of  the  most  convincing  is  that 
narrated  by  Adams  of  Aberdeen  and  summarized  by  Hess.^ 
Two  children  of  a  farm  laborer  died  of  tuberculous  meningitis 
in  January  and  March  of  1907.  There  was  no  known  expo- 
s-ure  to  the  disease  except  the  use  of  milk  from  a  cow  with 
tuberculosis  of  the  udder.  Bacilli  identical  in  type  with  those 
found  in  the  cow  were  recovered  from  the  cerebro-spinal  fluid 
of  one  of  the  children.  Most  of  the  cases  reported  are  not 
so  convincing  as  this,  and  in  many  the  evidence  is  decidedly 
weak  and  would  not  stand  critical  examination.  The  evidence 
afforded  by  these  cases  is  not  of  much  value,  for  though  some 
of  the  cases  are  doubtless  caused  in  the  manner  alleged,  they 
merely  indicate  what  is  also  suggested  by  animal  experiments, 
— the  possibility  of  human  infection  from  milk.  An  estima- 
tion of  the  extent  of  this  danger  must  be  made  in  other  ways. 

Proportion  of  Human  and  Bovine  Types.  —  Since  the  sig- 
nificance of  Theobald  Smith's  discovery  of  the  difference 
between  the  bovine  and  human  types  of  the  tubercle  bacillus 
has  been  recognized,  the  relative  frequ«icy  of  the  two  types 
in  human  beings  has  been  used  as  a  measure  of  the  impor- 
tance of  milk  infection,  for  it  is  conceded  that  it  is  through 
milk  almost  exclusively  that  bovine  tuberculosis  is  trans- 
mitted to  human  beings.  Much  care  and  labor  are  involved 
in  the  differentiation  of  the  two  types,  but  the  number  of 
observations  made  is  considerable,  among  which  those  of  the 
1  Hess,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1015. 


INFECTION  BY  FOOD  AND  DRINK  301 

German  and  British  commissions  are  notable.  Moss^  sum- 
marizes the  cases  previously  reported.  In  all  there  had  been 
306  cases  investigated,  in  63,  or  about  20  per  cent,  of  which 
bovine  bacilli  were  found.  But  it  must  not  be  inferred  from 
this  that  20  per  cent  of  all  cases  of  human  tuberculosis  would 
present  this  type.  With  the  exception  of  54  cases  in  adults 
studied  by  the  German  commission,  most  of  the  cases  have 
been  children  with  the  intestinal  or  glandular  forms  of  the 
disease.  In  the  54  adults  no  bovine  bacilli  were  found.  The 
bovine  type  of  bacillus  has  rarely  been  found  in  pulmonary 
tuberculosis,  even  among  children.  It  may  perhaps  be  in- 
ferred that  25  per  cent  of  bone  and  glandular  tuberculosis  in 
children  is  due  to  the  bovine  bacillus.  But  Tendeloo^  calls 
attention  to  the  fact  that  if  the  bovine  type  of  bacillus  is  a 
permanent  one,  —  and  unless  it  is  these  observations  are  of 
little  value,  — the  above  figures  are  probably  misleading,  for 
the  bovine  bacillus  if  permanent  will  be  transmitted  from 
man  to  man  and  does  not  always  indicate  a  bovine  origin. 
As  only  about  15  per  cent  of  the  tuberculosis  in  the  United 
States  is  of  the  form  in  which  the  bovine  bacillus  is  found, 
and  as  only  about  25  per  cent  of  the  cases  show  this  type  of 
bacillus,  we  are  justified,  using  the  type  as  a  test,  in  assuming 
that  only  about  5  per  cent  of  our  tuberculosis  is  derived  from 
bovine  sources.  But  this,  while  a  small  percentage,  would 
amount  to  almost  2500  deaths  annually  in  the  registration 
area  of  the  United  States,  —  certainly  a  number  which  ought 
to  be  considered. 

Epidemiological  Evidence.  —  It  seems  to  be  a  fact  I'.at 
tuberculosis,  even  those  forms  of  the  disease  which  arc  gen- 
erally supposed  to  be  caused  by  milk,  is  not  appreciably  less 
in  those  parts  of  the  world  where  cows'  milk  is  little  used,  or 
where  it  is  usually  sterilized,  or  where  there  is  little  tubercu- 
losis among  cattle.     Kitasato^  says  that  there  is  very  little 

1  Moss,  Johns  Hopkins  Hosp.  Bull.,  1909,  XX,  39. 

2  Tondeloo,  Sixth  Internat.  Cong,  on  Tuberc,  Wash.,  190S,  I,  87. 

^  Kitasato,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1904, 
XLVIII,  471. 


302       THE  SOURCES  AND  MODES  OF  INFECTION 

tuberculosis  among  the  cattle  in  Japan,  and  so  few  cows  that 
the  daily  milk  suppl}^  does  not  average  3  c.c.  per  capita,  yet 
nearly  8  per  cent  of  all  deaths  are  due  to  tuberculosis,  and  in 
a  series  of  autopsies  17  per  cent  of  the  tuberculosis  cases  were 
under  eighteen  years  of  age,  and  10  per  cent  of  the  cases 
showed  primary  intestinal  infection.  Cobb  says  that  substan- 
tially the  same  conditions  prevail  in  China.  According  to 
Heymann^  tuberculosis  is  very  common  in  Greenland,  where 
no  cows'  milk  is  used.  Fisch^  states  that  on  the  Gold  Coast 
no  milk  is  used,  yet  12  per  cent  of  the  sick  have  tuberculosis. 
Tuberculosis  prevails  as  extensively  in  Cuba  as  in  the  United 
States,  but  Dr.  Guiteras  tells  me  that  milk  is  practically 
never  used  without  scalding,  and  tuberculosis  is  comparatively 
rare  among  cattle.  If,  as  appears  from  a  study  of  the  relative 
prevalence  of  the  two  types  of  bacilli,  less  than  5  per  cent  of 
all  tuberculosis  is  due  to  cows'  milk,  the  entire  elimination  of 
this  factor  would  not,  as,  from  the  data  furnished  by  Japan, 
Cuba,  and  other  places,  it  appears  that  it  does  not,  have  any 
appreciable  effect  on  the  death  rate  from  this  disease.  The 
total  elimination  of  bovine  tuberculosis,  so  far  from  "stamp- 
ing out  the  great  white  plague,"  as  some  assert,  would  prob- 
ably not  make  any  noticeable  difference  in  the  tuberculosis 
death  rate.  Nevertheless  it  appears  from  present  evidence 
that  in  the  aggregate  a  large  number  of  deaths  are  due  to 
this  cause,  and  if  there  is  any  practical  method  of  reducing 
this  cause  of  death,  effort  should  be  made  to  apply  it. 

Protection  against  Tuberculous  Milk.  —  Various  ways  are 
suggested  for  eliminating  this  danger^  from  milk.  Among 
these  is  the  heating  of  milk  to  a  sufficient  temperature  to  kill 
tubercle  bacilli  as  well  as  typhoid  bacilli  and  other  pathogenic 
organisms.  Some  have  urged  compulsory  pasteurization  by 
dealers,  and  this  practice  is,  without  any  legislation,  making 
rapid  progress  in  cities.     But,  as  is  shown  by  Hess  in  New 

1  Heymann,  Ztschr.  f.  Hyg.  ii.  Infectionskrankh.,  Leipz.,  1904, 
XLVIII,  45. 

*  Fisch,  Cor.-Bl.  f.  schweiz.  Aerzte,  1904,  XXXIV,  761. 


INFECTION  BY  FOOD  AND  DRINK  303 

York,  commercial  pasteurization  does  not  always  destroy 
tubercle  bacilli,  and  the  proposition  that  commercial  pas- 
teurization be  under  the  control  of  health  officials  is  a  timely 
one.  As  has  already  been  stated,  there  are  objections  to  the 
compulsory  pasteurization  of  all  milk  sold,  hence  the  federal 
Department  of  Agriculture^  has  suggested  a  classification  of 
market  milk  into  — 

First.  Certified  milk,  which  presumal:^y  would  be  free 
from  danger  and  of  high  quality,  and  would  be  sold  at  a 
higher  price  to  those  who  desired  it. 

Second.  Inspected  milk,  which  also  should  be  from  cows 
free  from  tuberculosis,  but  which  would  not  show  so  low  a 
bacterial  count  as  the  certified  milk  and  which  could  be  sold 
for  not  much  if  any  more  than  the  next  class. 

Third.  All  milk  not  produced  under  such  rigid  inspection 
should  be  pasteurized  under  municipal  supervision. 

There  certainly  is  a  tendency,  without  any  compulsion,  for 
municipal  milk  supplies  to  become  classified  in  the  way  above 
indicated.  Another  way  of  removing  the  danger  is  for  the 
consumer  to  heat  the  milk  after  it  is  received  from  the  dealer. 
In  this  way  each  consumer  can  protect  himself  from  the  dan- 
ger of  contracting  tuberculosis,  typhoid  fever  and  similar 
diseases.  But  most  persons  will  not  do  this  unless  they  are 
induced  to  do  so  by  a  slow  process  of  education,  and  this 
education  can  scarcely  be  hastened  without  causing  an 
unreasonable  fear  of  milk,  which  will  result  in  lessening  the 
consumption  of  a  cheap,  digestible  and  nutritious  article  of 
food.  It  seems  to  me  that  what  is  needed  is  a  better  and 
more  exact  knowledge  of  the  relations  of  milk  to  disease  on 
the  part  of  health  officers  and  physicians,  from  which  ought 
to  follow  a  gradual  education  of  the  public,  but  without  an 
alarmist  propaganda,  and  then  there  will  probably  gradually 
develop  a  specialization  in  the  milk  business  to  meet  the 
necessarily  different  needs  of  different  people. 

1  U.  S.  Pub.  Health  &  Mar.  Hosp.  Scrv.,  Hyg.  Lab.,  Bull.  No.  41, 
559. 


304       THE  SOURCES  AND  MODES  OF  INFECTION 

Eradication  of  Bovine  Tuberculosis.  —  Another  way  of 
dealing  with  the  tuberculous  milk  problem  is  to  strive  to  eradi- 
cate bovine  tuberculosis,  or  at  least  to  eliminate  from  herds 
of  milch  cows  all  animals  in  the  active  stage  of  the  disease. 
This  is  urged  by  many,  and  has  been  and  is  being  attempted. 
It  is  claimed  by  the  federal  and  state  departments  of  agricul- 
ture that  the  existence  of  bovine  tuberculosis  entails  great  loss 
upon  the  farmers,  and  if  this  is  true,  these  departments  should 
devise  and  urge  means  for  eliminating  the  disease,  but  the 
expense  should  be  borne  by  the  farmers  and  not  by  the  public. 
If,  however,  the  restriction  or  elimination  of  bovine  tubercu- 
losis is  urged  as  a  public  health  measure,  as  it  so  often  is,  we 
should  count  well  the  cost  before  placing  it  upon  the  general 
taxpayer.  We  ought  to  have  a  finer  sense  of  financial  per- 
spective in  sanitary  matters.  The  cost  of  efficient  measures, 
if  efficient  measures  have  yet  been  devised,  for  eliminating 
bovine  tuberculosis  will  be  enormous,  and  we  may  well  con- 
sider whether  as  good  results  from  a  public-health  standpoint 
may  not  be  secured,  say  by  pasteurizing  milk,  and  whether 
the  money  might  not  be  expended  in  other  ways  with  far 
greater  results.  It  is  very  doubtful  whether  the  expenditure 
of  $100,000  a  year  for  several  years  in  a  state  like  Massachu- 
setts would  really  result  in  stamping  out  the  disease  in  cattle ; 
but  consider  how  much  such  a  sum  would  accomplish  if  spent 
in  the  establishment  of  dispensaries  and  the  employment  of 
district  nurses,  with  perhaps  $5000  to  $10,000  used  for  fur- 
ther scientific  study  of  the  many  unsolved'problems  connected 
with  the  causation,  prevention  and  cure  of  the  disease. 

Tubercle  Bacilli  in  Butter.  —  From  what  is  known  of  the 
viability  of  the  tubercle  bacillus,  there  can  be  no  doubt  that 
it  will  live  for  some  time  in  butter.  Schroeder  and  Cotton^ 
carefully  investigated  the  subject  and  found  virulent  tubercle 
bacilli  in  butterafter  three  months,  and  Trask^  refers  to  a  large 

1  Schroeder  and  Cotton,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Circ. 
No.  127,  1898. 

2  Trask,  J.  Am.  M.  Ass.,  Chicago,  1908,  LI,  1491. 


INFECTION  BY  FOOD  AND  DRINK  305 

number  of  similar  observations.  Cases  of  tuberculosis  do  not 
seem  to  have  been  traced  to  the  consumption  of  such  butter, 
and  it  is  very  unlikely  that  they  would  be  traced  even  if  they 
occurred.  Owing  to  the  small  amounts  of  butter  consumed, 
it  is  probable  that  very  few  cases  of  tuberculosis  are  caused 
in  this  waj'.  Butterine  also  has  been  sho\Mi  to  be  infected 
from  the  milk,  fat  and  butter  of  which  it  is  made.*  Owing 
to  the  mode  of  making  and  the  time  occupied  in  curing 
cheese,  virulent  tubercle  bacilli  are  probably  rarely  if  ever 
found  in  it.^ 

Mediterranean  Fever  from  Milk.  —  Mediterranean  fever, 
which  is  an  important  disease  around  the  shores  of  the 
Mediterranean,  has  been  considered  on  a  previous  page,  and 
reference  made  to  the  brilliant  researches  of  Bruce,  Horrocks 
and  others,  who  determined  that  it  is  primarily  a  disease  of 
goats,  and  only  incidentally  transmitted  to  man  through  the 
medium  of  milk.  The  obvious  remedy  is  to  avoid  the  use  of 
goats'  milk  whenever  these  animals  are  known  to  be  infected, 
and  in  the  Malta  garrison  the  disease  has  by  this  means  been 
eliminated.  It  is  rather  surprising  that  in  view  of  the  known 
facts  the  United  States  Department  of  Agriculture  should  in 
1905  have  imported  a  large  number  of  goats  from  Malta, 
but  the  importation  resulted  in  a  complete  demonstration  of 
the  infectiousness  of  the  milk,  for  quite  a  number  of  persons  on 
the  ship,  and  one  in  America,  developed  the  fever  as  a  result 
of  drinking  the  milk.     The  goats  have  now  all  been  killed. 

Anthrax  from  Milk.  —  Experiments  have  shouTi  that 
anthrax  bacilli  may  be  absorbed  through  the  intestines, 
and  they  are  found  in  the  milk  of  diseased  animals.'  In- 
stances of  this  mode  of  infection  in  man  have  been  reported, 
but  they  are  certainly  very  rare.^ 

»  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  1907,  XXIV,  152. 

'  Harrison,  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  1902,  XIX,  217. 

'  Horrocks,  J.  Roy.  Army  Med.  Corps,  Lond.,  1908,  XI,  46. 

*  Teacher,  J.  Comp.  Path.  &  Thcrap.,  Edinb.  <fe  Lond.,  1906,  XIX, 
225;  Meyer,  Deutsche  med.  Wchnschr.,  1908,  XXXIV,  108;  J.  Hyg., 
Cambridge,  1909,  IX,  279,  315. 


306       THE  SOURCES  AND  MODES  OF  INFECTION 

Foot-and-Mouth  Disease.  —  Foot-and-mouth  disease  is 
said  to  be  transmitted  to  human  beings  by  means  of  milk, 
and  according  to  Salmon  such  cases  are  frequently  reported 
in  European  outbreaks/  but  none  occurred  during  the  last 
outbreak  in  Massachusetts,  perhaps  owing  to  the  fact  that 
suitable  precautions  were  taken.  An  instance  of  thig  sort  of 
infection  occurred  near  Boston  in  1871.'  Kober  ^  refers  to 
other  instances  of  the  transmission  of  foot-and-mouth  disease 
by  milk. 

Rabies  from  Milk. — According  to  Kober,^  Nocard  proved 
experimentally  that  rabies  could  be  conveyed  in  milk,  and 
Burdach  infected  animals  with  the  milk  of  a  woman  sick  with 
the  disease  at  the  Pasteur  Institute.  Repetto^  was  able  to 
kill  rats  by  feeding  them  with  rabies  virus,  and  Remlinger" 
did  the  same.  Dr.  Austin  Peters  of  Boston  writes  me  that 
"  Several  times  where  cows  have  had  rabies  I  have  had  milk 
taken  from  them  and  brought  to  the  Harvard  Medical  School. 
Rabbits  and  guinea  pigs  inoculated  with  it  have  never  devel- 
oped rabies.  From  this  I  should  say  that  there  is  very  little 
danger  of  rabies  being  carried  through  the  milk." 

Other  Animal  Disease  and  Milk. — As  regards  actinomycosis, 
botryomycosis,  tetanus,  cowpox  and  many  other  animal 
diseases,  little  or  nothing  is  known  about  their  transmission 
by  milk. 

Diarrhea  from  Milk.  —  The  diarrhea  of  infants  is  prob- 
ably not  a  specific  disease,  but  the  group  of  disturbances 
which  pass  under  this  name  are  likely  to  be  due  to  infection  by 
a  number  of  organisms,  and  perhaps  to  some  extent  to  intoxi- 
cation with  the  products  of  bacterial  growth  outside  of  the 

1  U.  S.  Dept.  Agric,  Rep.  Bu.  An.  Ind.,  1902,  XIX,  405. 

2  Marion,  J.  Mass.  Ass.  Bds.  Health,  Bost.,  1903,  XIII,  11. 

3  Kober,  Milk  in  Relation  to  Public  Health,  Senate  Doc.  No.  441, 
57th  Congress,  First  Session,  1902,  154. 

*  Kober,  Idem,  157. 

^  Repetto,  Compt.  rend.  Soc.  blol.,  Paris,  1908,  LXIV,  716;  Abst. 
Am.  J.  Pub.  Hyg.,  Bost.,  1909,  XIX,  426. 

6  Remlinger,  Compt.  rend.  Soc.  de  biol.  Par.,  1908,  LXV,  385. 


INFECTION  BY   FOOD  AND  DRINK  307 

body.  Among  the  bacteria  suspected  of  causing  diarrhea 
are  B.  coli,  B.  enteritidis  sporogenes,  B.  enteritidis  (Gartner), 
B.  dysenterioe,  B.  paratyphosus  and  Streptococcus  enteritidis. 

The  summer  diarrheas  are  confined  principally  to  infantile 
life,  the  chief  incidence  falling  on  the  last  half  of  the  first 
year.  According  to  Newsholme^  they  are  associated  with  a 
deficient  rainfall,  and  their  dependence  upon  a  high  tempera- 
ture is  particularly  marked.  A  very  large  proportion  of  the 
deaths  occur  during  the  hot  summer  months,  and  the  hotter 
the  season,  as  a  general  thing,  the  higher  the  mortality.  The 
relation  between  temperature  and  this  disease  is  probably 
more  or  less  indirect,  and  at  present  is  not  well  understood. 
Another  marked  characteristic  of  the  summer  diarrheas  is 
that  they  are  intimately  associated  with  the  mode  of  feeding. 
Breast-fed  infants  are  very  little  affected,  while  artificially 
fed  infants  suffer  severely.  As  the  artificial  food  of  infants 
is  chiefly  cows'  milk,  and  as  these  diseases  appear  to  be  of 
bacterial  origin,  and  as  the  growth  of  bacteria  in  milk  is 
enormously  facilitated  by  hot  summer  weather,  it  is  generally 
assumed  that  diarrhea  is  due  to  the  growth  of  infective  organ- 
isms in  the  milk.  Some,  however,  doubt  the  validity  of 
this  assumption.  Liefmann^  considers  that  artificial  feeding 
causes  disturbances  of  digestion  and  nutrition,  and  that  these 
lay  the  foundation  and  open  the  way  for  new  and  injuri- 
ous factors.  The  latter  are  mostly  bacterial,  and  the  bacteria 
effect  an  entrance  into  the  child's  body  in  various  ways, 
usually  by  contact  infection,  and  not  so  often  by  milk  as  has 
been  commonly  supposed.  He  says  that  the  use  of  sterilized 
milk  is  disappointing,  Which  indicates  that  milk  is  not  the 
chief  vehicle  of  the  infection. 

Epidemiological  Studies.  —  In  1901-02  a  very  valuable 
series  of  observations  was  undertaken  in  New  York  by 
Park  and  Holt,  under  the  auspices  of  the  Rockefeller  Insti- 

»  Newsholme,  Pub.  Health,  Lond.,  1899-1900,  XII,  139. 
2  Liofmann,  Ztsrhr.  f.   Ilyjj;.  u.   Infpctionskrankh.,  Leipz.,  1908-09, 
LXII,  199;  Abat.  Pub.  Health,  1909,  XXH,  430. 


308       THE  SOURCES  AND  MODES  OF  INFECTION 

tute.^  It  appeared  to  these  observers  that  lack  of  care  in  the 
feeding  and  general  management  of  the  babies  had  more  to  do 
with  the  development  of  diarrhea  than  had  the  character  of 
the  milk.  It  is  true  that  exceptionally  dirty  store  milk  gave 
worse  results  than  any  other,  but  the  users  of  this  milk  were 
poorer  and  dirtier  and  gave  less  intelligent  care  to  their 
children.  A  rather  limited  number  of  children  were  fed  on 
fairly  good  milk  raw,  and  another  group  on  the  same  milk 
pasteurized,  other  conditions  being  nearly  the  same.  Those 
on  pasteurized  milk  had  much  less  diarrhea,  but  the  authors 
state  that  a  considerable  percentage  do  quite  as  well  on  raw 
milk.  Condensed  milk  was  found  to  be  associated  with  a 
large  percentage  of  diarrheal  cases.  Intelligent  care  and  feed- 
ing seem  to  the  authors  more  important  than  the  character 
of  the  milk.  They  also  consider  the  infection  of  the  milk  in 
the  home  or  store  as  a  very  important  factor.  Breast-fed 
babies  are  not  immune  to  diarrhea,  and  Newsholme,^  in  a 
very  careful  study  of  the  subject  at  Brighton,  found  that  6.6 
per  cent  of  the  deaths  from  diarrhea  were  in  breast-fed  infants, 
who  almost  certainly  could  not  have  been  infected  by  the 
milk.  Newsholme  pertinently  asks  why,  if  these  cases  were 
not  due  to  milk,  should  it  be  assumed  that  all  the  artificially 
fed  infants  who  succumbed  to  diarrhea  met  their  death  because 
of  milk  contamination.  From  a  study  of  the  kinds  of  milk  used 
in  Brighton  it  was  found  that  more  diarrhea  was  associated 
with  the  use  of  condensed  milk  than  with  that  of  any 
other.  Similar  results  from  the  use  of  condensed  milk  were 
found  by  Richards  in  the  neighboring  city  of  Croydon,^  and 
by  Sandilands  in  Finsbury,  London,^  and  their  findings  do 
not  differ  materially  from  those  of  Park  and  Holt.  In  the 
English  cities  a  very  good  brand  of  condensed  milk,  viz. 
Nestles',  was  the  one  chiefly  employed,  and  Sandilands  found 

'  Med.  News,  N.  Y.,  1903,  LXXXIII,  10G6. 
2  Newsholme,  J.  Hyg.,  Cambridge,  1906,  VI,  139. 
'  Rep.  Med.  Off.  Health,  Croydon,  1904,  1908. 
4  Sandilands,  J.  Hyg.,  Cambridge,  1906,  VI,  77. 


INFECTION  BY  FOOD  AND  DRINK  309 

it  very  free  from  bacteria.  He  also  states  that  this  condensed 
milk  is  collected  and  put  up  in  Switzerland  in  such  a  manner 
as  to  make  infection  during  the  process  much  less  likely  than 
in  ordinary  market  milk.  All  the  writers  above  referred  to 
consider  that  these  facts  indicate  that  the  infective  material 
of  infantile  diarrhea  gets  into  the  milk  and  other  food  to  a 
large  extent  in  the  home.  Newsholme  especially  insists  on 
this,  and  he  attributes  not  a  little  to  direct  contact.  Tomp- 
kins/ from  a  study  of  the  very  local  distribution  of  the  disease 
in  Leicester,  concluded  that  it  must  have  its  source  in  local 
conditions.  Robertson  and  Niven,  from  a  study  of  cases  in 
their  respective  cities  of  Birmingham  and  Manchester,  believe 
that  the  infection  takes  place  in  the  city  chiefly,  either  by 
direct  infection  or  through  the  milk. 

Explosive  Outbreaks  of  Diarrhea.  —  Sometimes  what 
appear  to  be  explosive  milk-borne  outbreaks  of  diarrhea 
occur.  Several  such  are  referred  to  by  Newman."  Recently 
a  very  interesting  outbreak  of  this  kind  has  been  reported 
by  Hay.  Various  bacteria,  such  as  B.  coli,  B.  enteritidis 
sporogenes  and  B.  enteritidis  of  Gartner,  have  been  isolated 
from  the  milk  in  such  cases  and  also  from  the  evacuations 
of  the  patients.  It  is  uncertain  whether  such  outbreaks  have 
any  connection  with  ordinary  summer  diarrhea,  though  that 
they  have  is  the  view  of  Delepine,^  and  he  believes  that  the 
contamination  of  milk  usually  takes  place  at  the  farm. 

Prevention  of  Diarrhea.  —  It  appears,  then,  that  we  have 
very  little  accurate  knowledge  as  to  the  causation  of  infantile 
diarrhea.  It  certainly  has  some  intimate  relation  to  the  diet, 
but  exactly  what  is  not  known.  We  do  know,  however,  that 
the  most  efficient  means  we  have  of  com})ating  it  is  correct 
feeding.  Breast  feeding  is  far  superior  to  anything  else,  but 
good  success  can  be  obtained  with  the  careful  and  scientific 

1  Tompkins,  Brit.  M.  J.,  I^nd.,  1889,  II,  180. 
«  Newman,  Infant  Mortality,  Lond.,  1006,  170. 
»  Hay,  Pub.  Iloaith,  Lond.,  1910,  X.XIII,  180. 
*  Delepine,  J.  Hyg.,  Cambridge,  1903,  III,  89. 


310       THE  SOURCES  AND  MODES  OF  INFECTION 

use  of  good  cows'  milk.  Pasteurized  milk  appears  to  be  better 
than  dirty  raw  milk  of  high  bacterial  count,  but  there  does 
not  seem  to  be  any  definite  connection  between  the  disease 
and  an  increasing  bacterial  content.  The  longer  milk  re- 
mains exposed  in  shops  and  houses,  the  more  dangerous  it 
seems  to  be.  Almost  all  who  have  had  to  do  with  modern 
milk  stations,  either  those  using  pasteurized  milk  or  those 
dispensing  clean  raw  milk,  agree  that  the  larger  part  of  the 
resulting  good  is  due  to  the  education  of  the  mother  in 
the  care  of  her  child.  The  chief  thing,  then,  is  to  teach  the 
mothers  how  to  modify,  keep  and  feed  milk.  It  is  of  impor- 
tance, too,  that  the  mothers  should  be  enabled  to  get  fairly 
clean  and  fresh  milk.  In  some  cities  it  is  doubtless  necessary 
to  establish  milk  stations  for  this  purpose,  which  dispense 
either  pasteurized  milk,  or  preferably  clean  raw  milk.  In 
Providence  stations  were  found  to  be  unnecessary,  as  there  is 
no  part  of  the  city  in  which  it  is  not  possible  to  get  18  to  24 
hours'  old  milk  with  less  than  50,000  bacteria  per  c.c,  and  a 
number  of  dealers  furnish  milk  below  10,000.  This  milk  is 
sold  by  the  producer  in  glass  bottles  and  at  the  ordinary 
market  price.  The  milk  is  by  no  means  equal  to  certified 
milk,  but  the  observations  of  Park  and  Holt,  and  our  expe- 
rience in  Providence,  seem  to  show  that  milk  of  the  grade 
above  indicated  is  ordinarily  as  little  likely  to  cause  infantile 
diarrhea  as  is  certified  milk.  Only  a  small  amount  of  the  milk 
supply  of  a  city  is  used  for  feeding  infants,  and  it  seems  un- 
necessary to  insist  on  a  high  grade  of  expensive  milk  for  all 
consumers.  At  present  it  is  more  economical  to  bring  the 
existing  good  supplies  to  the  knowledge  of  the  mothers 
through  physicians,  the  health  department,  district  nurses 
and  milk  stations.  In  cities  up  to  200,000  or  300,000  it  is 
probable  that  enough  dealers  can  be  found  to  supply  the 
necessary  demand  for  a  good  though  not  certified  milk. 


INFECTION  BY  FOOD  AND   DRINK  311 

Infection  by  Meat. 

Inspection  of  meat  is  considered  by  the  public  a  matter  of 
the  greatest  importance,  but  concerning  many  forms  of  meat 
infection  we  have  httle  definite  knowledge,  and  the  danger  of 
others  has  been  greatly  exaggerated,  not  only  by  the  public, 
but  also  by  physicians  and  health  officials.  Various  animal 
parasites,  such  as  tapeworms  and  trichinae,  are  derived  from 
the  lower  animals  through  the  use  of  their  flesh  as  food,  but 
a  consideration  of  these  is  beyond  our  present  purpose.  One 
of  these  animal  parasites,  the  trichina,  is  quite  common  in 
pork,  and  a  considerable  number  of  deaths  are  caused  by  it 
each  year. 

Food  Poisonings.  —  What  are  commonly  called  food  poi- 
sonings, when  resulting  from  eating  meat,  are  due  to  two 
general  causes.  One  class  is  the  result  of  the  action  of  various 
kinds  of  putrefactive  organisms  which  infect  the  food  after 
slaughter.  These  cases  we  need  not  consider.  Another  class 
results  from  infection  of  the  flesh  during  the  life  of  the  animal, 
and  is  due,  so  far  as  kno\vn,  to  various  members  of  the  colon 
group,  such  as  B.  paratyphosus,  B.  enteritidis  (Gartner)  and 
B.  morbificans.  In  many  instances  this  unwholesome  meat  is 
derived  from  diseased  animals,  usually  showing  some  sort  of 
enteritis  or  septic  infection.  That  the  infection  is  always 
derived  from  diseased  animals  seems  unlikely,  for  several 
observers  have  found  in  healthy  animals  the  bacteria  which 
are  believed  to  be  the  cause. ^  Savage,"  however,  was  un- 
able to  isolate  B.  enteritidis  (Gartner)  from  the  intestines  of 
23  healthy  animals  which  he  carefully  studied.  But  from 
what  is  known  of  the  relations  of  this  group  of  bacteria  to 
human  beings  we  should  expect  to  find  them  occasionally  in 
healthy  animals,  convalescents  and  carriers.  Unfortunately 
the  toxins  produced  by  these  bacteria  are  not  always  de- 

1  Bolduan,  Food  Poisoning,  New  York,  190P,  33. 
»  Savage,  Rep.  Med.  Off.  of  Local  Gov.  Bd.,  1906-07,  XXXVI,  253; 
1907-08,  XXXVII,  425. 


312       THE  SOURCES  AND  MODES  OF  INFECTION 

stroyed  by  heat,  so  that  while  cooking  may  kill  the  bacteria, 
cooked  meat,  which  has  been  the  seat  of  bacterial  growth, 
has  been  known  to  cause  sharp  outbreaks  characterized  by 
acute  gastrointestinal  symptoms.  If  living  bacteria  of  this 
group  are  present,  infection  with  them  may  result,  causing  a 
slow  after  development  of  symptoms  somewhat  akin  to  those 
of  typhoid  fever.  The  cooking  of  meat  cannot  be  relied  upon 
wholly  to  prevent  sickness  arising  from  this  sort  of  food 
infection.  Government  inspection  is  suggested  as  the  only 
method  by  which  these  diseases  can  be  prevented.  If,  how- 
ever, bacilli  are  found  in  healthy  animals,  it  is  questionable 
whether  any  amount  of  inspection  would  entirely  eliminate 
the  danger.  How  great  the  danger  is  it  is  difficult  to  deter- 
mine. A  good  many  outbreaks  have  been  reported  in  Ger- 
many, aggregating  thousands  of  cases,  and  reports  come  not 
rarely  from  England.  No  data  are  available  for  the  United 
States.  For  several  years  I  have  been  on  the  lookout  for 
the  reports  of  such  cases  in  the  medical  press  and  in  the 
"Index  Medicus,"  and  one  year  I  employed  a  press-clipping 
bureau  to  secure  cuttings  from  the  lay  press,  but  I  have 
notes  of  scarcely  more  than  a  dozen  outbreaks.  Doubtless 
others  occurred,  but  they  cannot  have  been  very  numerous. 
A  good  many  reports  of  instances  of  "  ptomaine  poisoning  " 
find  their  way  into  the  newspapers,  which  prove  on  investi- 
gation to  have  no  basis  in  fact. 

Meat  and  Tuberculosis.  —  In  the  public  mind  the  fear  of 
contracting  tuberculosis  by  eating  meat  is  very  considerable, 
and  public  sentiment  is  sufficient  to  support  very  stringent 
regulation  of  the  sale  of  meat  from  diseased  animals.  Yet 
it  does  not  appear  that  there  is  a  single  recorded  instance  of 
the  transmission  of  disease  in  this  way.  And  we  should 
expect  that  if  such  were  possible  it  would  be  exceedingly  rare. 
Tubercle  bacilli  have  their  habitat  in  lungs,  liver,  intestines, 
glands  and  other  viscera,  and  not  usually  in  the  muscle  or 
fat.  The  tubercle  bacillus  is  easily  killed  by  heat,  and  very 
little  of  this  class  of  food  is  eaten  without  cooking.     Smoked 


INFECTION  BY  FOOD  AND  DRINK  313 

beef  and  ham  are  occasionally  eaten  without  cooking,  but  even 
then  considerable  time  is  consumed  in  the  process  of  corning 
and  smoking,  and  in  the  rare  cases  in  which  a  few  bacilli 
are  contained  in  the  meat  they  are  likely  to  have  lost  most 
of  their  virulence.  As  for  the  viscera,  if  they  are  used  at  all 
for  food  they  are  generally  pretty  well  cooked.  Cornet  states 
that  Schottelius  studied  the  use  of  meat  from  tuberculous 
animals  in  Wiirzburg,  and  could  not  find  a  case  of  the  disease, 
although  the  meat  was  eaten  in  every  form.  It  has  been 
said  that  while  tuberculosis  has  been  decreasing  the  consump- 
tion of  meat  has  been  increasing;  and  this  is  certainly  an 
indication  that  the  use  of  meat  cannot  be  a  factor  of  any 
great  moment  in  the  causation  of  the  disease.  At  the  most 
it  is  scarcely  possible  for  the  disease  to  be  derived  from  this 
source  except  in  rare  instances. 

Conclusions.  —  The  diseases  which  it  is  alleged  may  be 
transmitted  by  flesh  foods  are  those  caused  by  animal  para- 
sites, of  which  trichinosis  is  the  most  important,  diseased 
conditions  produced  by  the  colon  group  of  bacilli,  and  tuber- 
culosis. The  latter  is  a  negligible  quantity,  the  second  group 
probably  causes  very  few  deaths  in  this  country,  while  trichi- 
nosis is  doubtless  the  most  important  disease  transmitted  in 
this  manner. 

Federal  Control.  —  The  federal  government  has  instituted 
an  expensive  meat-inspection  service,  ostensibly  to  guard  the 
health  of  the  public,  but  as  trichinosis,  the  most  common  and 
serious  of  the  animal  diseases,  though  it  is  very  rare  in 
man,  is  ignored,  it  is  suspected  that  the  system  was  insti- 
tuted by  Congress  as  the  result  of  an  ill-informed  though 
popular  demand.  Filthy  conditions  in  the  slaughterhouses, 
and  the  killing  of  diseased  animals,  though  their  flesh  may 
not  be  injurious  to  health,  are  shocking  to  the  aesthetic  sense 
and  the  public  demands  reform.  Including  the  expense  of 
inspection  and  the  value  of  the  meats  condemned,  the  cost 
to  the  country  is  $5,000,000  or  $6,000,000  per  annum.  It  is 
true  that  the  conditions  of  labor  in  the  great  packinghouses 


314       THE  SOURCES  AND  MODES  OF  INFECTION 

have  been  improved,  and  that  cleanher  methods  of  handHng 
meat  have  been  enforced,  hut  it  is  doubtful  whether  any  sick- 
ness among  consumers  has  been  prevented.  I  cannot  help 
thinking  how  much  ultimate  good  might  have  accrued  if  a 
tenth  of  the  sum  spent  in  meat  inspection  had  been  devoted 
to  the  systematic  study  of  the  many  unsolved  problems  of 
sanitation,  such  as,  for  instance,  the  danger  from  fomites,  the 
part  played  by  air  in  the  spread  of  disease,  the  causes  of 
the  decline  of  tuberculosis  and  the  mode  of  extension  of  the 
disease,  the  relation  of  food  to  health,  the  causes  of  infantile 
diarrhea,  the  relation  of  water  supplies  to  the  general  health, 
or  the  meaning  of  bad  air  and  its  effect  on  health. 

Infection  by  Shellfish. 

Oysters.  —  Since  oysters  and  other  shellfish  are  often 
eaten  raw,  and  often  live  in  sewage-polluted  waters,  they 
might  be  suspected,  and  indeed  were  suspected  by  Sir  Charles 
Cameron  as  long  ago  as  1880,  of  being  the  cause  of  typhoid 
fever,  and  in  1893  Thorne  suggested  that  the  sporadic  cases 
of  cholera  which  appeared  here  and  there  in  England  were 
due  to  the  eating  of  raw  shellfish  infected  at  the  mouth  of 
the  Humber.  The  first  demonstration  of  the  relation  of  shell- 
fish to  disease  was  by  Conn.^  He  showed  that  23  of  100 
students  who  went  to  a  certain  banquet  developed  typhoid 
fever,  probably  as  a  result  of  eating  oysters.  Of  those  who  did 
not  eat  raw  oysters  none  were  sick,  and  one  man  who  did  not 
go  to  the  banquet  ate  oysters  at  the  dealers'  and  also  was  sick. 
The  oysters  had  been  kept  about  300  feet  from  a  drain  leading 
from  a  house  where  there  was  typhoid  fever.  Similar  out- 
breaks have  been  reported  by  Chantemesse,^  Mosny,^  Chatin,* 

1  Conn,  Rep.  St.  Bd.  Health,  Connect.,  1895,  253;  Med.  Rec,  N.  Y., 
1894,  XLVI,  743. 

2  Chantemesse,  Bull.  Acad,  de  med.,  Par.,  1896,  3  s.  XXXV,  588, 
724. 

»  Mosny,  Rev.  d'hyg.,  1900. 

*  Chatin,  Semaine  med,  1897,  XVII,  91. 


INFECTION  BY  FOOD   AND   DRINK  315 

Thresh  and  Wood/  a  committee  which  studied  the  subject 
at  Atlantic  City,^  Fraser,^  Soper*  and  Morse, ^ 

Clams,  Mussels.  —  Clams  as  well  as  oysters  have  been 
believed  to  be  the  cause  of  outbreaks/  and  where  mussels 
and  cockles  are  consumed  raw  in  considerable  quanti- 
ties  they  are  equally  liable  to  carry  the  infecting  organ-' 
isms.  Three  outbreaks  in  Norwich,  England,  in  1908  were 
traced  to  mussels.^  Mussels  also  were  believed  to  be  the 
cause  of  an  outbreak  of  typhoid  fever  in  North  Ormsby,^ 
and  have  been  an  important  factor  in  the  causation  of 
typhoid  fever  in  Belfast. 

Shellfish  in  English  Cities.  —  Not  only  have  shellfish  been 
shown  to  be  the  cause  of  marked  outbreaks  of  illness,  as 
just  shown,  but  they  are  strongly  believed  by  many,  espe- 
cially by  English  health  officials,  to  be  an  important  source  of 
the  ordinary  "  residual  "  typhoid  fever  occurring  in  cities. 
Newsholme®  is  especially  insistent  on  this.  A  careful  study 
of  the  matter  in  Brighton,  where  he  was  then  health  officer, 
showed  that  in  1894-96,  of  189  reported  cases  of  typhoid  fever, 
41  were  imported,  and  of  the  148  remaining,  51,  or  nearly  30 
per  cent,  had  eaten  raw  oysters  or  mussels  within  the  incuba- 
tion period  of  the  disease.  These  shellfish  all  came  from 
grounds  which  were  contaminated  with  sewage.  From  1894 
to  1902,  of  643  reported  cases  of  typhoid  fever,  158  were  due 
to  eating  oysters  and  80  to  other  shellfish,  making  in  all  about 
37  per  cent  due  to  this  cause.  Similar  observations  and  con- 
clusions may  be  found  in  the  reports  of  the  health  officers 
of  Birmingham,  Leicester,  Southend,  Manchester,  London, 

1  Thresh  and  Wood,  Lancet,  Load.,  1902,  I!,  1567. 

2  Phila.  M.  J.,  1902,  X,  634. 

»  Fraser,  Lancet,  Lond.,  1903,  I,  183. 

*  Soper,  Med.  News,  N.  Y.,  1905,  LXXXVI,  241. 

*  Morse,  Rep.  St.  Bd.  Health,  Ma.s.s.,  1900,  836. 
«  Plowright,  Brit.  M.  J.,  Ix)nd.,  1900,  II,  681. 

'  Rep.  on  Sanitary  Condition  of  Norwich,  1908,  14. 

»  The  Medical  Officer,  1909,  II,  131. 

'  Newsholme,  J.  San.  Inst.,  Lend.,  XVII. 


316       THE  SOURCES  AND  MODES  OF  INFECTION 

Portsmouth  and  other  places.  The  tj^phoid  death  rate  in 
English  cities  is  low  and  health  officials  find  it  difficult  to 
account  for  the  origin  of  the  cases.  The  pollution  of  shellfish 
with  sewage  is  not  uncommon  around  the  English  and  Irish 
coasts.^  A  considerable  percentage  of  the  cases  of  typhoid 
fever  are  known  to  have  eaten  shellfish,  often  from  polluted 
sources,  within  two  to  four  weeks  of  the  date  of  attack. 
Perhaps  the  assumption  is  justifiable  that  some  of  these  cases 
at  least  are  due  to  the  shellfish.  Typhoid  fever  has  for  some 
time  been  rather  prevalent  in  Belfast,  and  a  special  commis- 
sion was  appointed  for  its  investigation.  This  commission 
believes  that  the  chief  source  of  the  disease  is  mussels  and 
cockles,  picked  up  by  the  poorer  people  along  the  sewage- 
polluted  flats.^  Mair^  states  that  in  Belfast  it  was  impossible 
to  make  a  satisfactory  canvass  of  the  number  of  mussel  users, 
either  among  the  general  population  or  among  the  typhoid 
patients.  He  bases  his  conclusions  as  to  the  part  played  by 
mussels  on  a  careful  statistical  study,  and  shows  that  the 
disease  in  Belfast  has  varied  according  to  changes  in  the 
amount  of  mussels  consumed.  He  also  shows  that  Jews  and 
the  wea:lthier  classes,  who  use  no  mussels,  had  Httle  typhoid 
fever.  Nash^  states  that  at  Southend  54  per  cent  of  the 
typhoid-fever  cases  confessed  to  the  eating  of  shellfish,  while 
only  0.4  per  cent  of  501  sick  with  other  diseases  confessed  to 
such  eating.  Since  the  consumption  of  raw  shellfish  has 
decreased,  typhoid  fever  has  decreased  also.  In  Leicester,' 
50  per  cent  of  the  tj'phoid  cases  ate  mussels,  but  they  were 
used  in  only  15  per  cent  of  a  small  number  of  non infected 
houses.     Johnston®  found  that  25.8  per  cent  of  62  persons 

1  Rep.  Med.  Off.  Loc.  Gov.  Bd.,  1894-9,5,  XXIV;  Loc.  Gov.  Bd.  for 
Ireland,  Rep.  on  Shellfish  Layings,  1904. 

2  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Pub.  Health  Rep.,  Wash., 
1908,  XXIII,  995. 

'  Proe.  Roy.  Soc.  Med.,  Lond.,  1909,  II,  Epidem.  Sect.,  187. 

'  Nash,  Pub.  Health,  Lond.,  190.3-05,  XVI,  80. 

'  Rep.  Med.  Off.  Health,  Leicester,  1908,  31. 

'  Johnston,  The  Medical  Officer,  II,  1909,  431. 


INFECTION  BY  FOOD  AND  DRINK  317 

with  typhoid  fever  had  eaten  shellfish,  mussels  and  peri- 
winkles within  a  short  time  of  their  illness,  while  of  827 
other  persons  only  7.3  per  cent  had  eaten  them  during  the 
whole  summer.  In  the  United  States,  also,  non-epidemic  or 
"  residual  "  typhoid  has  been  attributed  to  the  use  of  raw 
oysters,  as  in  New  York.^  The  chief  reason  for  this  seems 
to  be  that  there  is  known  to  be  a  considerable  consumption 
of  sewage-infected  oysters."  ^Nlost  of  the  beds  on  which 
oysters  are  grown  are  free  from  dangerous  pollution,  but  it 
is  quite  common  to  "  fatten,"  i.e.,  freshen  and  swell  them,  in 
estuaries  near  sewer  openings. 

Danger  Variable.  —  It  seems  reasonable  to  conclude  that 
the  danger  from  eating  sewage-infected  shellfish  is  a  real  one. 
Exactly  how  great  it  is,  is  difficult  to  determine.  In  England 
an3rwhere  from  15  to  50  per  cent  of  the  disease  in  cities  is 
attributed  to  eating  raw  mussels  or  oysters,  but  this  is  on  the 
supposition  that  every  typhoid  patient  who  has  recently  eaten 
raw  shellfish  derived  the  disease  from  that  source.  In  Provi- 
dence raw  oysters  are  very  popular;  they  are  consumed  in 
restaurants  in  large  numbers,  and  form  a  course  in  a  large 
proportion  of  banquets  and  dinners.  Many  o\'sters  are 
grown  in  the  upper  part  of  the  bay,  in  water  grossly  contami- 
nated with  sewage,  and  in  the  water  and  in  the  oysters 
colon  bacilli  are  found.  Until  within  two  or  three  years, 
numbers  of  oysters  from  clean  water  have  been  "fattened" 
near  sewer  openings,  yet  Providence  has  a  typhoid  death 
rate  less  than  half  that  of  the  average  American  city.  Oys- 
ters are  not  eaten  to  any  extent  in  August,  when  typhoid 
fever  begins  to  increase,  and  they  are  largely  consumed  in 
the  winter  and  spring,  when  there  is  little  of  the  disease. 
During  the  years  1902-05,  of  263  typhoid-fever  patients  who 

•  Med.  News,  N.  Y.,  1904,  LXXXIV,  325;  1905,  LXXXV,  571. 

'  Report  of  U.  S.' Commissioner  of  Fisheries  for  year  ending  Jan.  30, 
1904,  .Appendix,  189;  Rep.  Dept.  Health,  City  of  N.  Y.,  1904,  I,  313; 
Rep.  St.  Bd.  Health,  New  Jersey,  1904,  226;  Rep.  Dept.  Health,  Balti- 
more, 1907,  124. 


318       THE  SOURCES  AND  MODES  OF  INFECTION 

replied  definitely  as  to  wliether  they  had  eaten  oysters,  only 
26,  or  about  10  per  cent,  said  that  thej^  had.  Very  few  raw 
oysters  are  eaten  by  laboring  people,  but  at  present  laboring 
people  furnish  fully  their  share  of  typhoid  fever. 

While  the  amount  of  typhoid  fever  due  to  the  use  of  raw 
shellfish  is  not  very  great,  this  danger  ought  to  be  eliminated 
entirely,  and  state  boards  of  health  should  have  the  authority 
to  forbid  the  sale  of  shellfish  from  polluted  waters. 

Crawfish  and  Typhoid  Fever.  —  Dr.  Bissell  of  Buffalo 
wrote  to  me  about  an  interesting  local  outbreak  of  typhoid 
fever  which  was  at  first  suspected  to  be  due  to  milk.  But 
further  investigation  showed  that  it  was  confined  chiefly  to 
boys,  and  that  these  boys  were  in  the  habit  of  catching  craw- 
fish from  a  lake  grossly  polluted  with  sewage.  After  par- 
tially cooking  the  crawfish  before  an  open  fire  in  the  field, 
the  boys  would  eat  them. 

Infection  by  Fried  Fish. 

In  1900,  Hamer  '  of  London  reported  outbreaks  of  typhoid 
fever  in  Southwark,  Lambert  and  Kensal-town  which  seemed 
to  be  confined  in  each  case  to  the  customers  of  certain  fried- 
fish  shops.  While  the  sickness  was  believed  to  be  due  to 
the  eating  of  fish,  no  conclusion  was  reached  as  to  how  the 
fish  became  infected.  It  is  scarcely  possible  that  infection  of 
the  fish  before  cooking  should  not  be  destroyed  by  the  pro- 
cess, and  yet  it  seems  unlikely  that  handling  by  carriers  after 
infection  could  cause  such  an  outbreak. 

Infection  by  Watercress. 

In  the  summer  of  1903  there  was  a  very  considerable  out- 
break of  typhoid  fever  in  Hackney,  London.^  This  was  very 
carefully  investigated  by  Warry,  and  he  eliminated  all  articles 
of  food  and  drink  as  sources  of  the  infection,  except  water- 
cress.    Of  the  110  cases  55.3  per  cent  ate  watercress  which 

1  Hamer,  Special  Rep.  to  Med.  Off.  Health,  Lond.,  1900. 

2  Warry,  Rep.  Med.  Off.  Health,  Lond.,  1903,  35. 


'   INFECTION  BY  FOOD  AND  DRINK  319 

grew  in  sewage-polluted  water.  An  inquiry  showed  that  the 
incidence  of  the  disease  on  watercress  caters  was  three  times 
as  great  as  upon  those  who  did  not  eat  it. 

Infection  hy  Celery. 

Morse  ^  reports  an  outbreak  of  typhoid  fever  due  to  the 
use  of  celery.  There  were  49  cases  in  an  insane  asylum. 
Nearly  all  of  these  belonged  to  the  class  of  pay  patients,  to 
whom  alone  celery  was  served.  Several  other  persons,  how- 
ever, had  access  to  the  celery  and  contracted  the  disease. 
There  were  no  cases  except  four  contact  cases  among  non- 
users  of  celery.  There  had  been  typhoid  fever  in  the  insti- 
tution some  months  before  and  the  celery  bed  had  received 
the  hospital  sewage.  The  disease  developed  soon  after  the 
celery  came  into  use. 

^  Morse,  Rep.  St.  Bd.  Health,  Mass.,  1899,  761. 


CHAPTER  VIII. 

INFECTION   BY    INSECTS. 

Importance  of  Subject.  —  The  subject-matter  of  this  chap- 
ter is  of  the  utmost  importance  in  the  practical  work  of  pre- 
ventive medicine,  and  it  is  of  equal  interest  to  the  student  of 
scientific  epidemiology.  Our  actual  knowledge  of  the  insect 
carriers  of  disease  has  all  been  acquired  during  the  last  fif- 
teen or  twenty  years,  and  marks  as  brilliant  and  successful 
an  epoch  in  the  history  of  medicine  as  did  the  phenome- 
nal development  of  bacteriology  in  the  years  immediately 
preceding. 

I  hesitate  very  much  to  discuss  the  subject  at  all,  as  most 
of  the  diseases  considered  are  essentially  tropical,  and  of 
tropical  diseases  I  have  had  no  personal  knowledge.  But 
even  we  who  dwell  in  temperate  regions  are  likely  to  meet 
with  isolated  cases  of  tropical  diseases,  or  to  suffer  from 
occasional  invasions  of  yellow  fever,  bubonic  plague  and 
relapsing  fever.  In  any  event,  it  is  important  that  both  the 
student  of  preventive  medicine  and  the  health  officer  keep 
informed  as  to  current  progress  in  this  line  of  research,  and 
ever  bear  in  mind  the  possibility  that  insects  may  play  a 
part,  at  least,  in  the  spread  of  those  diseases  with  which  he 
is  more  familiar. 

Modes  of  Transmission.  —  There  are  various  ways  in 
which  disease  may  be  transmitted  by  insects.  The  most 
interesting  and  to  us  novel  manner  in  which  this  happens  is 
that  the  discovery  of  which  we  owe  to  Theobold  Smith,  in 
which  the  insect,  as  well  as  the  higher  animal,  serves  as  the 
true  host  of  the  pathogenic  organism  which  causes  the  disease. 
Most  of  the  diseases  transmitted  in  this  way  are  probably 
caused  by  animal  parasites,  usually  protozoa.     As  a  rule, 

320 


INFECTION   BY   INSECTS  321 

they  propagate  asexually  only  in  man  or  the  higher  animals, 
but  develop  sexual  forms  in  insects,  which  thus  become,  zoo- 
logically considered,  their  true  hosts,  while  man,  if  it  be  a 
human  disease,  is  the  intermediate  host.  The  insects  in  such 
instances  are  sometimes  called  biological  carriers.  In  other 
cases  the  parasites  do  not  develop  in  the  insect,  which  is  then 
merely  a  mechanical  carrier,  as  would  be  a  lancet  or  a  h3'po- 
dermic  syringe.  The  classification  of  insect-borne  diseases  is 
far  from  definite,  owing  to  the  present  fragmentary  condition 
of  our  knowledge.  We  will  first  consider  those  diseases  which 
appear  to  be  biologically  carried  by  insects. 

First  Proof  of  Transmission  by  Insects.  —  Although  there 
had  previously  been  suggestions  that  disease  might  be  trans- 
mitted by  insects,  the  first  definite  proof  was  the  demonstra- 
tion in  1893  by  Smith  and  Kilborne  ^  of  the  development  of 
Piroplasma  higeminum  and  the  part  played  by  ticks  in  the 
transmission  of  Texas  cattle  fever.  This  discovery  did  much 
to  point  out  the  lines  on  which  experimental  work  should 
proceed.  These  authors  demonstrated  the  presence  of  the 
Piroplasma  in  the  blood  of  infected  cattle  and  in  the  ticks 
which  fed  upon  them.  They  also  showed  that  the  ticks  trans- 
mit the  germ  through  their  eggs  to  their  progeny.  The 
new  generation  of  infected  ticks  then  become  attached  to 
cattle,  and  by  their  bites  inoculate  them  and  cause  the  disease. 
It  was  demonstrated  that  there  could  be  no  infection  of  the 
fields  or  fodder,  either  by  the  excreta  of  cattle  or  by  dead 
ticks  or  ova.  The  living  tick  is  necessary  for  the  transmis- 
sion of  the  disease,  and  doubtless  the  Piroplasma  passes 
through  definite  phases  of  its  development  in  the  body  of  the 
tick.  Smith  and  Kilborne  showed  not  only  that  ticks  trans- 
mit this  disease,  but  also  that  it  is  transmitted  only  in  this 
way.  They  furthermore  showed  that  apparently  healthy  cat- 
tle might  be  carriers  of  the  Piroplasma,  and  therefore  in  the 
presence  of  ticks  could  cause  the  spread  of  the  disease.     Texas 

'  Smith  and  Kilborne,  U.  S.  Dept.  Agric,  Bu.  An.  Ind.,  Bull.  1, 
1893. 


322       THE  SOURCES  AND   MODES  OF   INFECTION 

cattle  fever,  though  of  immense  economic  importance  in  the 
cattle-raising  industry,  is  not  transmissible  to  human  beings. 
The  great  importance  of  Smith  and  Kilborne's  discovery,  from 
our  present  point  of  view,  is  the  encouragement  it  gave  to  the 
study  of  the  transmission  of  human  diseases  by  insect  agen- 
cies. Koch  has  demonstrated  a  similar  connection  between 
ticks  and  a  disease  of  cattle  in  German  East  Africa  caused  by 
another  species  of  Piroplasma,  —  P.  parvum.  Nuttall  and 
Graham-Smith  ^  have  investigated  a  similar  disease  in  dogs, 
also  transmitted  by  ticks,  and  have  described  the  devel- 
opment of  the  parasite  P.  canis.  Christophers  also  ^.  has 
studied  the  development  of  this  parasite.  There  appears 
to  be  no  doubt  that  piroplasmosis  of  horses  and  sheep  is 
transmitted  by  ticks. 

Malaria. 

Discovery  of  Insect  Transmission.  —  While  Nott,^  King,^ 
Laveran,"  Koch  and  others  had  suggested,  on  epidemiological 
grounds,  that  this  disease  might  be  insect  borne,  it  was  not 
until  1895  that  Ross,®  stimulated  by  the  work  of  Manson 
on  filariasis,  watched  the  development  of  the  malarial  parasite 
in  mosquitoes  which  had  been  allowed  to  bite  persons  sick 
with  the  disease.  As  Manson  had  already  shown  that  in 
filariasis  it  is  only  a  particular  species  of  mosquito  which 
can  serve  as  host  for  the  filaria,  Ross  suspected  that  the 
same  might  be  true  of  human  malaria,  and  he  finally  deter- 
mined that  it  was  only  in  individuals  of  the  genus  Anopheles 
that  the  malarial  parasite  can  develop.     Ross  ^  now  turned 

»  Nuttall  and  Graham-Smith,  J.  Hyg.,  Cambridge,  1904,  1905,  1906, 
1907. 

2  Christophers,  Brit.  M.  J.,  Lond.,  1907,  II,  1333. 

3  Nott,  N.  Orl.  M.  &  S.  J.,  1847-48,  IV,  563. 

*  King,  Tr.  Philos.  Soc,  Wash.,  1883. 

5  Laveran,  Le  Paludisme,  Paris,  1891,  147. 

*  Ross,  Abst.  by  Manson,  Lancet,  Lond.,  1896,  I,  831. 

^  Ross,  Rep.  on  the  Cultivation  of  Proteosoma  Labbe  in  Grey  Mos- 
quitoes, Indian  M.  Gaz.,  Calcutta,  1898,  XXXIII,  133,  401,  448. 


INFECTION  BY  INSECTS  323 

to  the  study  of  the  malaria  of  birds  due  to  a  Proteosoma,  and 
he  demonstrated  that  the  disease  could  be  transmitted  from 
bird  to  bird  by  the  bites  of  mosquitoes.  The  parasites  of  the 
disease  are  taken  up  with  the  blood  by  the  insect  in  the  act 
of  biting,  and  after  undergoing  sexual  multiplication,  spread 
through  the  insect,  and  are  found  in  the  salivary  gland, 
whence  they  are  injected  into  the  next  bird  bitten.  Mean- 
while Grassi  in  Ital}^  had  come  to  the  conclusion,  from  a  study 
of  the  distribution  of  different  species  of  mosquitoes,  that 
Anopheles  was  one  of  the  forms  likely  to  transmit  the  disease. 
Bignami  had  previously  been  unsuccessful  in  transmitting 
malaria  by  the  bites  of  mosquitoes,  chiefly  because  he  experi- 
mented largely  with  Culex  instead  of  Anopheles.  Finally 
Grassi,  Bignami  and  Bastianelli  in  1899  caused  malaria  in 
human  beings  by  allowing  anopheles  mosquitoes  to  bite  them 
some  days  after  they  had  bitten  other  individuals  sick  with 
malaria.  To  avoid  the  criticism  that  these  experiments  were 
carried  on  in  Italy,  an  intensely  malarial  country,  where 
natural  infection  could  not  be  absolutely  excluded,  Patrick 
Manson  ^  had  a  number  of  infected  mosquitoes  sent  from 
Italy  to  England  in  1900,  and  caused  two  men,  Dr.  Thurburn 
Manson  and  Mr.  Warren,  who  had  never  been  in  a  malarial 
region,  to  be  bitten.  Both  men  developed  malaria  in  exactly 
eighteen  days.  In  the  same  year  Sambon  and  Low  lived  for 
three  months  in  the  most  malarial  section  of  the  Roman 
Campagna,  protecting  themselves  absolutely  against  the  bites 
of  mosquitoes,  but  taking  no  other  precautions.  They  did 
not  contract  malaria,  but  of  fifteen  or  sixteen  police  sent  from 
Rome,  who  spent  one  night  unprotected  in  the  same  place, 
every  one  developed  the  disease." 

Mosquito  Sole  Carrier  of  Malaria.  —  The  observations 
and  experiments  above  noted  prove  conclusively  that  malaria 
is  transmitted  by  the  bites  of  infected  anopheles  mosquitoes, 
but  do  not  indicate  whether  or  not  it  may  be  spread  in  other 

1  Patrick  Manson,  Brit.  M.  J.,  Lond.,  1900,  II,  949. 
«  Sambon  and  Low,  Brit.  M.  J.,  Lond.,  1900,  II,  1679. 


324       THE  SOURCES  AND  MODES  OF  INFECTION 

ways.  It  was  Manon's  theory  at  first  that  the  malarial  para- 
site is  transmitted  from  adult  to  larvse  by  means  of  the  water 
in  which  the  eggs  are  laid,  and  that  this  water  is  also  the 
means  of  infecting  human  beings.  He  suggested  that  germs 
might  be  inhaled  in  dust  from  dried-up  and  infected  pools. 
As  regards  transmission  by  water  the  experiments  of  Celli  ^ 
and  others  have  already  been  referred  to,  which  indicate  that 
such  a  mode  of  transference  is  highly  improbable,  and  there 
is  certainly  no  epidemiological  evidence  in  its  favor.  That 
the  Plasmodium  of  malaria  grows  outside  of  the  animal  body 
is  also  improbable,  for  it  has  never  been  possible  as  yet  to 
cultivate  it  in  any  way."  It  has  never  been  found  in  the  water 
of  malarial  regions.^  Even  if  there  are  sporelike  forms  resist- 
ant to  drying,  there  is  strong  evidence  that  such  are  not  air- 
borne, for  mosquito  netting  would  in  no  way  interfere  with  the 
free  movement  of  particles  small  enough  to  be  wafted  by  the 
air;  but  abundant  evidence  has  shown  that  efficient  screening 
against  mosquitoes  affords  complete  protection  against  this 
disease,  even  in  the  most  intensely  malarial  regions.  More- 
over the  success  attending  methods  of  prevention  based  on 
the  mosquito  theory  point  indubitably  to  the  truth  of  the 
theory.  Experimental,  clinical  and  epidemiological  evidence 
combine  to  demonstrate  that  malaria  is  a  disease  transmitted 
solely  by  the  bites  of  infected  mosquitoes.  There  are  several 
forms  of  malarial  fever,  such  as  tertian,  quartan,  aestivo-au- 
tumnal,  apparently  caused  by  different  species  of  Plasmo- 
dium, but  there  is  no  need  here  of  considering  these  different 
forms  and  their  relation  one  to  another.  Suffice  it  to  say  that 
the  mosquito  appears  to  be  the  true  host  of  this  parasite,  and 
in  its  body  it  undergoes  sexual  reproduction.  From  eight  to 
ten  days  after  the  mosquito  is  infected,  its  entire  body,  in- 
cluding its  salivary  gland,  becomes  infested  with  the  so-called 
sporozoite  forms,  and  when  these  are  injected  into  human  be- 

1  See  chapter  on  Infection  by  Water. 

2  Craig,  The  Malarial  Fevers,  New  York,  1909,  93. 
^  Craig,  idem,  83. 


INFECTION  BY  INSECTS  325 

ings  theycontinue  to  undergo  a  vegetative  or  asexual  prolifera- 
tion, the  successive  phases  of  which  give  rise  to  the  symptoms 
of  the  disease.  It  is  believed  that  no  vertebrate  other  than 
man  serves  as  the  host  of  the  Plasmodium,  and  until  recently 
it  was  thought  that  no  mosquitoes  except  those  belonging  to 
the  genus  Anopheles  could  transmit  the  disease;  but  recent 
observations  in  the  Philippines  ^  indicate  that  a  mosquito 
breeding  in  salt  marshes,  Myzomyia  ludlowii,  may  become  the 
host  of  the  Plasmodium.  But  it  is  certain  that  almost  alwaj's 
it  is  some  species  of  Anopheles  which  is  the  carrier.  Not  all 
Anopheles,  however,  can  serve  as  the  host,  for  one  of  our 
common  species  in  the  northern  United  States,  A.  puncti- 
pennis,  does  not." 

Habits  of  Mosquitoes. — Mosquitoes  develop  only  in  water. 
The  larval  and  pupal  stages  may  occupy  from  eight  days  to  a 
number  of  weeks,  or  the  larvse  may  even  live  all  winter 
under  the  ice  in  northern  regions,  or  retain  their  vitality  for 
some  time  in  the  dried  mud  of  the  tropics.  The  mature 
insects  usually  live  only  a  few  weeks,  but  in  northern  regions 
hibernate  during  cold  weather.  The  habits  of  life  of  the  dif- 
ferent species  of  Anopheles  vary  considerably,  and  should  be 
carefully  studied  when  measures  for  extermination  are  under- 
taken. Only  the  adult  female  bites,  so  she  alone  is  the  carrier 
ofthedisea.se.  Anopheles  usually  bite  at  night.  Gorgas^  states 
that  they  do  not  usually  fly  above  100  yards,  and  that  clearing 
and  draining  the  area  within  this  distance  of  houses  affords 
great  protection.  Nevertheless  it  sometimes  happens  that 
under  favorable  conditions  the  insects  may  be  carried  a  con- 
siderable distance  by  the  wind.  Craig  ^  states  that  they  may 
be  borno  ovon  two  and  one-half  miles. 

Must  be  Many  Mosquitoes.  —  Mosquitoes  are  not  infected 
with  the  malarial  parasite  unless  they  bite  infected  human 

»  Banks,  Philippine  J.  Sc.  [B.  Med.],  1908,  III,  335. 

»  Hirgchberg,  Johns  Hopkin.s  Hosp.  Bull.,  Bait.,  1904,  XV,  53. 

'  Gorgaa,  J.  Am.  M.  .\s.s.,  Chicago,  1909,  LII,  1967. 

*  Craig,  The  Malarial  Fevers,  New  York,  1009,  69. 


326       THE  SOURCES  AND   MODES  OF  INFECTION 

beings.  The  number  of  infected  mosquitoes,  then,  varies  with 
the  number  of  infected  persons  to  whom  they  have  access. 
Craig  ^  refers  to  the  findings  of  himself  and  others  as  varying 
from  35  per  cent  to  0.6  per  cent.  For  the  spread  of  malaria  it 
is  necessary  that  there  should  be  Anopheles  and  human  beings 
infected  with  the  parasites.  But  if  the  mosquitoes  are  not 
numerous  and  the  cases  of  infection  are  not  numerous,  the 
chances  of  a  mosquito  becoming  infected  and  then  biting 
another  victim  after  a  proper  interval  are  not  great,  so  that  it 
may  happen  that  there  may  be  mosquitoes  and  human  infec- 
tion without  extension  of  the  disease.  Thus  it  is  not  known 
that  cases  of  malaria  have  ever  developed  on  the  island  of 
Rhode  Island,  but  I  havefoundafew^wop/^eZes breeding  there, 
and  with  the  great  numbers  of  summer  visitors  from  all  over 
the  world,  and  many  soldiers,  and  sailors  of  the  navy,  it  is 
probable  that  the  malarial  parasite  is  frequently  present  on 
the  island.  These  epidemiological  facts  led  me  for  some  time 
to  suspect  that  the  supposed  mode  of  transmission  of  this 
disease  above  outlined  did  not  contain  the  whole  truth;  but 
the  directness  and  strength  of  the  experimental  proof,  and, 
above  all,  the  success  of  mosquito  control  in  checking  the 
disease  render  it  certain  that  practically  the  onl}^  way  in 
which  malarial  disease  is  caused  is  by  the  bites  of  mosquitoes. 
There  are  numberless  interesting  details  connected  with  the 
life  history  and  habits  of  the  mosquito  which  are  of  great 
importance  but  which  cannot  be  considered  here.  The  way 
in  which  these  habits  explain  the  peculiarities  in  the  develop- 
ment of  malaria  is  well  considered  by  Nuttall.' 

Ways  of  Prevention.  —  There  are  several  ways  in  which 
the  spread  of  malarial  disease  may  be  checked. 

First.  Quinia.  —  The  administration  of  the  various  salts  of 
quinia  prevents  the  development  of  the  malarial  parasite  in 
the  blood,  and  this  drug  is  an  extremely  valuable  remedy  in 
the  prevention  and  cure  of  malaria.     Antitoxin  and  vaccines 

^  Craig,  loc.  cit.,  74. 

»  Nuttall,  Johns  Hopkins  Hosp.  Rep.,  Bait.,  1899,  VIII,  78, 


INFECTION  BY  INSECTS  827 

are  of  great  value  in  the  prevention  and  cure  of  certain  of  the 
infectious  diseases,  as  diphtheria,  typhoid  fever  and  cholera, 
but  they  are  of  value  chiefly  to  the  individual.  The  difficulties 
attendant  upon  their  administration  are  so  great  that  they 
cannot  be  used  except  in  rare  instances  to  protect  large  bodies 
of  people.  The  antitoxins,  too,  probably  do  not  prevent  the 
growth  of  the  germs  which  are  the  cause  of  the  disease,  so 
that  in  a  way  their  use,  as  for  instance  that  of  diphtheria 
antitoxin,  may  actually  in  some  instances  favor  the  spread  of 
the  disease,  by  preventing  the  development  of  symptoms 
when  the  bacilli  are  present,  thus  making  a  "carrier"  instead 
of  a  "case,"  and  carriers  are  always  difficult  to  control.  It  is 
otherwise  with  quinia.  This  drug  actually  kills  the  Plas- 
modium or  drives  it  out  of  the  circulation  and  out  of  the 
way  of  the  mosquito,  and  so  not  only  protects  the  individual 
but  prevents  him  from  becoming  a  focus  of  infection.  Quinia 
is  not  only  universally  used  as  a  specific  curative  agent,  but  it 
is  also  employed  in  large  quantities  as  a  prophylactic,  and  its 
employment  in  this  manner  is  considered  a  valuable  means  of 
fighting  the  disease,  reducing  as  it  does  the  number  of  foci  of 
infection.  Indeed  Koch  and  some  others  claim  that  this  is 
the  only  way  in  which  malaria  can  be  eradicated,  as  mosquito 
destruction  is  in  many  places  impossible.  All  workers  in  this 
field  employ  quinia  for  this  purpose,  though  there  is  con- 
siderable discussion  as  to  its  mode  of  administration,  which 
varies  from  15  grains  every  eight  days,  as  used  by  Koch,  to 
3  grains  daily,  as  advised  by  Gorgas.  This  subject  is  fully 
discussed  by  Craig,^  who  states  that  in  the  vast  majority  of 
instances  2j  grains  (0.15  grm.)  daily  is  sufficient  to  prevent 
malarial  infection.  It  is  difficult  to  estimate  the  value  of  a 
particular  prophylactic  measure,  for  one  measure  is  rarely 
used  alone,  but  there  is  little  doubt  of  the  great  efficiency  of 
quinia  in  the  fight  against  malaria.  Craig  states  that  at 
Camp  Stotsenburg,  in  the  Philippines,  measures  directed 
against  mosquitoes  had  little  result  until  supplemented  by 
»  Craig,  The  Malarial  Fevers,  New  York,  1909,  343. 


328       THE  SOURCES  AND  MODES  OF  INFECTION 

the  daily  administration  of  quinia.  Koch  and  his  followers 
also  report  excellent  results  from  the  use  of  quinia  alone. 
Celli,^  while  urging  every  method  directed  against  the  mos- 
quito, considers  that  in  Italy  experience  has  shown  that  the 
daily  administration  of  quinia  has  been  the  most  effective 
measure  in  reducing  the  number  of  deaths  from  malaria, 
which  have  fallen  steadily  from  13,861  in  1901  to  4871  in  1906, 
during  which  year  20,723  kilos  of  quinia  were  sold. 

Second.  Isolation  of  Persons.  —  The  attempt  may  be 
made  to  isolate  the  infected  persons  so  that  the  mosquitoes 
may  not  pass  from  them  to  the  healthy.  This  may  be  accom- 
plished in  various  ways.  In  many  tropical  regions  where 
the  native  population,  or  at  least  the  native  children,  are 
always  infected,  the  dwellings  of  the  natives  and  the  sus- 
ceptible Europeans  are  separated  a  sufficient  distance  to 
escape  the  ordinary  excursions  of  the  mosquitoes. 

Sometimes  the  patients,  if  few  in  number,  are  screened  from 
mosquitoes  in  their  own  homes  or  are  removed  to  screened 
hospitals.  This  is  very  commonly  done  with  the  imported 
cases  which  come  to  Havana,"  and  in  Panama  many  malarial 
patients  are  treated  in  the  screened  hospitals.  Others  are 
cared  for  in  their  own  well-screened  houses. 

To  assist  in  this  measure  it  is  desirable  to  kill  all  mosquitoes 
in  the  house  which  may  have  bitten  the  patient  before  the 
disease  was  recognized  or  reported  to  the  authorities.  Gor- 
gas  considers  sulphur  dioxid  the  best  for  this,  but  as  this 
cannot  be  used  in  an  occupied  room,  pyrethrum  may  be 
burned,  which  so  stupefies  the  insects  that  they  may  be  easily 
swept  up  from  the  floor.  Celli  has  given  much  study  to  this 
class  of  culicides  and  recommends  one  or  two  tablespoonfuls 
of  a  mixture  of  the  unexpanded  flowers  of  chrysanthemum 
and  valerian  root. 

Third.  Screening. —  Effort  should  be  made  in  all  malarious 
regions  to  protect  susceptible  persons  from  the  bites  of  mos- 

1  Quoted  by  Craig,  The  Malarial  Fevers,  New  York,  1909,  345. 
8  Guiteras,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIU,  1165. 


INFECTION  BY  INSECTS  329 

quitoes.  The  screening  of  the  whole  house  is  the  most  impor- 
tant step.  Copper  netting  is  the  cheapest  in  the  end,  and  it 
should,  according  to  Craig,  have  11  meshes  to  2  cm.  Gorgas 
says  that  it  is  necessary  that  houses  should  be  screened  by 
persons  experienced  in  mosquito  work,  or  openings  are  sure 
to  be  left.  The  experiments  of  Sambon  and  Low  proved  the 
efficacy  of  this  method  of  prophylaxis,  and  Craig  states  that 
the  screening  of  the  houses  of  railway  employees  on  certain 
Italian  lines  has  been  as  effectual  a  method  as  the  administra- 
tion of  quinia.  Screening  is  carried  on  most  extensively  in 
the  Canal  Zone.  Craig  says  that  where  screening  is  impos- 
sible the  use  of  mosquito  canopies  over  the  beds  at  night  is 
a  very  useful  measure,  and  head  nets  and  gloves  for  men 
obliged  to  be  out  at  night  are  of  much  value.  By  the  use  of 
these  methods  the  percentage  of  malaria  among  troops  in 
Sardinia  was  reduced  from  70  to  20,  and  in  Formosa  no  mala- 
ria developed  among  1 15  soldiers  protected  by  netting,  while 
of  717  not  so  protected  251  were  attacked. 

The  removal  of  trees,  vines  and  shrubs  from  the  vicinity 
of  dwellings  is  considered  by  Gorgas  an  important  measure, 
as  these  serve  as  hiding  places  for  the  insects  by  day.^ 

A  certain  amount  of  protection  may  be  secured  by  the 
application  to  the  skin  of  substances  annoying  to  the  mos- 
quito, or  of  ointment  which  mechanically  interferes  with 
biting.  Oil  of  citronella  or  eucalyptus,  and  petroleum  or 
cocoanut  oil  or  vaseline,  are  used,  but  such  applications 
are  not  by  most  writers  considered  of  much  value. 

Fourth.  Mosquito  Pra^ention.  —  Theoretically  the  most 
effectual  way  to  eradicate  malaria  is  to  prevent  the  growth  of 
mosquitoes.  While  their  complete  destruction  is  not  usually 
possible,  its  attempt  must  always  take  first  rank  in  preventive 
measures.  The  fact  that  mosquitoes  are  a  great  nuisance, 
as  well  as  carriers  of  disease,  makes  still  more  desirable  their 
extermination  wherever  possible.  Large  sums,  in  certain 
parts  of  the  United  States,  are  being  expended  in  fighting  the 
»  Gorgas,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1967. 


330        THE  SOURCES  AND  MODES  OF  INFECTION 

salt-marsh  mosquito,  which  is  harmless  so  far  as  carrying 
disease  is  concerned. 

Fifth.  Draining.  —  When  mosquitoes  breed  in  pools  and 
swamps,  as  they  so  often  do,  draining  and  filling  must  be 
done.  If  water  cannot  be  entirely  gotten  rid  of,  the  banks  of 
streams,  ponds  and  ditches  must  be  straightened  and  deepened, 
and  freed  from  vegetation,  to  remove  hiding  places  for  the 
larvae  and  permit  their  destruction.  Gorgas  insists  upon  the 
importance  of  having  this  work  done  by  men  especially  trained 
for  it,  and  supervised  by  experts.  Ordinary  contractors  and 
laborers  are  sure  to  overlook  breeding  places  and  to  neglect  im- 
portant details  of  the  work.  Many  species  of  Anopheles  breed 
in  cisterns  or  accidental  receptacles  of  water  near  houses. 
Hence  all  such  should  either  be  removed  or  carefully  screened. 

Sixth.  Oiling. —  The  growth  of  larvae  in  water  can  be  pre- 
vented by  the  application  of  crude  petroleum  or  kerosene  to 
the  surface  at  the  rate  of  an  ounce  to  each  15  square  feet  of  sur- 
face. Various  poisonous  substances  may  be  added  to  the  water, 
as  hydrochloric  acid,  corrosive  sublimate,  formalin,  chloride 
of  lime  and  various  aniline  dyes.  Some  of  the  last  named 
are  strongly  recommended  by  Celli,as  they  are  harmless  to  the 
higher  animals.  The  use  of  quicklime  causes  a  glaze  on  the 
surface  which  is  a  protection,  and  sulphate  of  copper  kills  the 
algae  on  which  the  mosquitoes  live.  Most  fish  are  voracious 
feeders  on  the  larvae,  and  if  pools  and  streams  are  supplied 
with  fish,  and  kept  free  from  weeds,  mosquitoes  cannot  thrive. 
It  is  said  that  the  introduction  of  a  certain  small  fish  into 
the  streams  of  Barbados  caused  the  extermination  of  mos- 
quitoes.^ According  to  Craig,  the  application  of  cultures  of 
Aspergillus  niger  and  A.  glaucus  destroys  the  larvae. 

Success  of  Measures.  —  There  is  probably  scarcely  a 
locality  in  which  the  application  of  a  single  prophylactic 
measure  will  be  found  effectual  in  "  stamping  out  "  malaria, 
and  sometimes  all  methods  combined  fail  to  bring  success. 
Thus  at  Mian  Mir  in  India,  according  to  Craig,  the  most 
1  Ballou,  Nature,  Lond.,  1909,  LXXX,  16. 


INFECTION  BY  INSECTS  331 

careful  draining  and  oiling  were  followed  by  very  discourag- 
ing results.  On  the  other  hand,  preventive  measures  have  in 
many  localities  given  wonderfully  good  results.  The  success 
of  the  work  in  Italy,  a.s  reported  by  Celli,  has  already  been 
referred  to.  In  Havana  the  deaths  from  malaria  previous 
to  the  occupation  by  the  United  States  averaged  350  per 
annum,  rising  to  1907  in  1898.  The  measures  carried  out  by 
Gorgas  to  destroy  the  yellow-fever  mosquitoes  also  practi- 
cally eliminated  the  Anopheles,  and  the  deaths  now  average 
only  about  40,  and  three-fourths  of  these  are,  according  to 
Kean/  due  to  infection  contracted  elsewhere.  At  Ismailia  ^ 
the  cases  were  reduced  from  2284  in  1900  to  37  in  1905, 
chiefly  by  destroying  the  breeding  places  of  mosquitoes.  At 
Klang  and  Port  Swettenham  in  the  Federated  Malay  States 
99  per  cent  of  the  mosquitoes  were  eliminated,  with  a  corre- 
sponding decrease  in  malaria.  Ross  also  refers  to  the  success- 
ful reduction  of  malaria  at  Port  Said,  Durban,  Hong  Kong, 
Khartoum,  and  in  Candia,  St.  Lucia,  Greece  and  Algeria.^ 

Success  in  Panama.  —  To  my  mind  the  most  wonderful 
success  of  all  has  been  attained  by  Gorgas  in  the  Panama 
Canal  Zone.  Here  was  a  stretch  of  territory  45  miles  long, 
intensely  malarious,  nowoccupied  by  a  force  of  44,000  persons, 
mostly  foreigners.  The  rainfall  is  heavy,  and  the  work  of 
canal  building  alters  in  every  direction  the  configuration  of 
the  land  and  the  natural  drainage.  Malaria  caused  enor- 
mous losses  during  the  French  occupation  and  was  second 
only  to  yellow  fever  in  interrupting  the  work.  Mosquitoes 
have  been  entirely  eliminated  from  Colon,  a  town  of  15,000 
inhabitants,  and  the  death  rate  from  malaria  among  employ- 
ees was  only  1.34  per  thou.«;and  in  1908,  having  been  reduced 
from  5.57  in  1905.  Considering  the  tremendous  obstacles  to 
be  overcome,  this  success  is  certainly  astonishing.^ 

'  Kean,  .1.  .\m.  M.  Ass.,  1909,  LIII,  1166.  " 

"  Ross,  Lancet,  Lond.,  1907,  II,  879. 

»  RO.S.S,  Nature,  Lond.,  1909,  LXXX,  41.5. 

*  Gorgas,  J.  Am.  M.  Ass.,  Chicago   1909,  LII,  1967. 


332       THE  SOURCES  AND  MODES  OF  INFECTION 


Yellow  Fever. 

History  of  Discovery.  —  Nott  appears  to  have  been  the 
first  (1848)  to  attribute  to  mosquitoes  a  role  in  the  causation 
of  yellow  fever,  but  this  was  merely  a  suggestion  which  re- 
ceived little  attention.  According  to  Cruz/  Beauperthuy 
published  on  the  23d  of  May,  1854,  in  the  Official  Gazette  of 
Cumana,  Venezuela,  an  article  which  expounded  with  great 
clearness  a  mosquito  theory  of  this  disease.  But  to  Finlay 
of  Havana  is  due  the  credit  for  the  first  experimental  work,  a 
report  of  which  was  presented  to  the  Royal  Academy  of  Medi- 
cal, Physical  and  Natural  Sciences  in  Havana  in  1882.  Finlay 
continued  to  experiment  and  write  until  1900,  when  the 
American  Commission,  consisting  of  Reed,  Carroll,  Agra- 
monte  and  Lazear,  undertook  their  investigations  at  Havana.^ 
Finlay  had  come  to  the  conclusion  that  Culex  fasciatiis,  now 
Stegomyia  calopus,  was  the  species  of  mosquito  which  was 
likely  to  be  involved  in  the  transmission  of  the  disease.  After 
the  occupation  of  Cuba  by  the  United  States  in  1898,  the 
war  department  undertook  with  great  energy  the  extirpation 
of  yellow  fever  from  Havana.  At  that  time  the  disease  was 
believed  to  be  essentially  a  filth  disease,  and  the  energy  of 
the  government  was  directed  towards  making  Havana  clean, 
and  soon  its  "sanitary  condition"  vied  with  that  of  the  very 
best  cities  in  the  United  States.  At  the  same  time  the  most 
stringent  measures  of  isolation,  as  isolation  was  at  that  time 
understood,  were  applied.  But  yellow  fever  refused  to  be 
stamped  out,  and  in  1900  caused  1244  cases  and  310  deaths, 
many  of  them  among  the  "  best  people  "  in  the  cleanest  parts 
of  the  city.^  It  was  becoming  evident  that  the  old  theories 
were  not  satisfactory,  and  the  war  department  appointed  the 

1  Cruz,  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv.,  Pub.  Health  Rep., 
Wash.,  1909,  XXIV,  1741. 

2  Lee,  Am.  Pub.  Health  Ass.  Rep.,  190.5,  XXX,  8. 

'  Series  4,  Yellow  Fever  Pub.,  San.  Dept.,  Havana,  1902,  10. 


INFECTION  BY   INSECTS  333 

commission  above  referred  to,  which  proceeded  to  Havana 
and  in  its  earUest  work  put  Finlay's  mosquito  theory  to  the 
test.  They  were  not  a  Uttle  influenced  to  this  step  by  the 
observations  of  Carter.^  He  had  determined,  from  a  study 
of  the  disease  in  isolated  farmhouses,  that  from  nine  to  six- 
teen days  usually  elapse,  after  the  introduction  of  the  disease, 
before  the  house  can  infect  second  cases.  It  was  thought 
that  this  interval  might  depend  upon  a  period  of  incubation 
in  the  mosquito.  Owing  to  the  hearty  cooperation  of  General 
Wood,  the  governor,  himself  a  medical  man,  every  facility 
was  accorded  the  commission,  and  inoculation  experiments 
were  made  on  volunteer  human  subjects,  among  whom  was 
Lazear,  a  member  of  the  commission.  Of  1 1  persons  bitten 
by  mosquitoes  which  had  some  days  before  been  allowed  to 
feed  on  a  yellow-fever  patient,  2  developed  the  disease,  one 
of  whom  was  Lazear,  who  died  as  the  result  of  the  inoculation.^ 
Carroll  too  was  bitten  and  developed  the  disease.  As  critics 
suggested  that  natural  infection  could  not  be  excluded,  the 
experiments  were  repeated  in  November  and  December, 
1900,  under  more  convincing  conditions,  and  6  of  7  persons 
bitten  developed  typical  yellow  fever,  and  the  transmission 
of  the  disease  in  this  manner  was  demonstrated  beyond  ques- 
tion.^ Later  Guiteras  *  succeeded  in  inoculating  8  more  per- 
sons, which  made  a  total  of  24  persons  infected  by  the  bites 
of  mosquitoes.  Of  these  3  died,  and  the  post-mortem  ex- 
amination demonstrated  the  lesions  of  yellow  fever.  The 
commission  had  by  the  direct  transfer  of  blood  shown  that 
the  infective  agent  exists  in  that  fluid,  even  when  filtered.* 
All  the  experimenters  demonstrated  that  the  mosquito  could 
not  transmit  the  disease  until  six  to  eighteen  days  after 

1  New  Orleans  M.  &  S.  J.,  1900,  LII,  617. 

«  Am.  Puh.  Health  As.s.  Rep.,  1900,  XXVI,  37;  Phila.  M.  J.,  1900, 
VI,  790. 

'  Series  3,  Yellow  Fever  Pub.,  San.  Dept.,  Havana,  1902. 

*  Series  6,  Yellow  Fever  Pub.,  San.  Dept.,  Havana,  1902,  26. 

*  Am.  Med.,  Phila.,  1902,  III,  301. 


334       THE  SOURCES  AND  MODES  OF  INFECTION 

biting  a  yellow-fever  patient,  thus  explaining  the  wonder- 
fully accurate  clinical  observations  of  Carter.  Although  it 
has  been  shown  that  filtered  blood  contains  the  infective 
principle,  thus  far  it  has  not  been  demonstrated  by  micro- 
scopical or  cultural  methods.  It  seems  in  the  highest  degree 
probable,  from  this  very  remarkable  work,  that  the  exciting 
agent  of  yellow  fever  closely  resembles  that  of  malaria,  in 
that  it  is  found  in  the  blood,  is  taken  up  by  a  particular 
species  of  mosquito,  develops  in  the  mosquito  during  a  period 
of  some  days,  and  is  then  transmitted  to  new  subjects  only 
by  the  subsequent  bites  of  the  insect. 

Transmission  by  Fomites  Disproved.  —  Belief  in  the  infec- 
tiousness of  the  vomitus  and  excreta  and  in  the  important 
part  played  by  fomites  in  the  extension  of  the  disease  was 
so  firmly  fixed  that  it  seemed  necessary  to  test  this  theory 
by  actual  experiment.  The  commission  for  this  purpose 
exposed  a  number  of  non-immune  persons  to  the  closest 
possible  contact,  during  a  period  of  two  weeks,  to  bedding, 
clothing  and  other  articles  all  grossly  contaminated  with 
supposedly  infective  material,  but  none  of  them  contracted 
the  disease.  Later  Guiteras,  while  carrying  on  his  mosquito  in- 
oculations, incidentally  exposed  many  non-immunes  to  fabrics 
that  had  been  in  close  touch  with  yellow-fever  cases,  but  with 
like  negative  results ;  and  again  Gorgas,  at  Las  Animas  Hos- 
pital in  Havana,  put  the  fomites  theory  to  test  in  the  most 
thorough  manner  by  the  exposure  of  non-immunes  to  close 
and  continued  contact.^ 

Even  before  these  demonstrations,  some  acute  observers, 
especially  Carter,^  had  concluded  from  epidemiological  studies 
that  fomites  played  little  part  in  the  dissemination  of  this 
disease.  Carter  showed  among  other  things  that  countless 
pieces  of  baggage,  many  of  them  certainly  from  infected 
houses  in  Cuba  and  Vera  Cruz,  had  passed  to  northern  ports 
without  causing  yellow  fever  in  a  single  instance. 

*  Series  3,  Yellow  Fever  Pub.,  San.  Dept.,  Havana,  1902,  22. 

*  Carter,  Med.  News,  N.  Y.,  1904,  LXXXV,  878. 


INFECTION  BY  INSECTS  335 

Transportation  of  Mosquitoes.  —  Theoretically  there  is  no 
reason  why  infected  mosquitoes  might  not  occasionally  be 
carried  in  baggage,  but  admission  of  baggage  without  dis- 
infection, without  any  known  instance  of  the  development  of 
yellow  fever,  shows  that  such  a  mode  of  transmission  must 
be  extremely  rare.  Even  the  carriage  of  infected  mosquitoes 
in  vessels  must  be  unusual,  though  instances  are  recorded  by 
Carter  '  and  others.  Grubbs  -  found  Stegomyia  calopus  on 
three  of  sixty-five  vessels  entering  the  Gulf  Quarantine  Sta- 
tion. Souchon,^  at  New  Orleans,  found  that  2.5  per  cent  of 
the  mosquitoes  caught  on  incoming  steamers  from  Havana 
or  the  West  Indies  were  Stegomyia  calopus.  Probably  none 
of  these  were  infected. 

The  rapid  and  brilliant  demonstration  of  the  true  mode  of 
extension  of  3'ellow  fever  was  immediately  followed  by  an 
equally  rapid  and  brilliant  application  of  the  new  knowledge. 
Two  months  after  the  termination  of  the  commission's  ex- 
periments, Gorgas  was  as  energetically  applying  the  new 
methods  of  yellow-fever  control  in  Havana  as  he  had  pre- 
viously devoted  himself  to  cleansing  the  city,  and  within 
eight  months  the  Stegomyia  calopus  had  been  nearly  exter- 
minated, and  Havana  was  free  from  the  disease  for  the  first 
time  in  150  years. 

Habits  of  Yellow-fever  Mosquito.  —  Different  species  of 
mosquitoes  have  different  habits  of  life,  and  Stegomyia  calopus 
is  much  more  of  a  domestic  mosquito  than  are  the  Anopheles. 
It  prefers  to  breed  in  clean  rain  water,  but  will  grow  in  any 
water  that  is  not  too  muddy.  It  may  even  be  found  in  cess- 
pools and  in  gutters,  but  its  favorite  home  is  the  rain-water 
cistern,  barrel,  jar  or  other  container  which  is  usually  pro- 
vided for  every  house.  It  seems  to  prefer  dark,  covered  recep- 
tacles. The  adult  mosquito  is  rather  feeble  and  rarely  flies  far. 

»  Carter,  Med.  Rec,  N.  Y.,  1902,  LXI,  441. 

^  Grubbs,  Yellow  Fever  Institute,  U.  S.  Pub.  Health  &  Mar.  Hosp. 
Serv.,  Bull.  No.  11. 

»  Souchon,  J.  Am.  M.  Ass.,  Chicago,  1903,  XL,  1647. 


336       THE  SOURCES  AND  MODES  OF  INFECTION 

Preventive  Measures.  —  The  defensive  measures  against 
yellow  fever  must  of  course  be  somewhat  like  those  directed 
against  malaria,  but  differ  in  some  important  particulars. 
The  most  important  of  these  is  that  there  is  no  drug  which 
will  prevent  and  cure  this  disease  as  quinia  does  malaria. 
Another  point  of  difference  is  that  yellow  fever  is  not  nearly 
so  widespread  a  disease  as  is  malaria,  and  that  it  is  an  acute 
disease  in  which  the  patient  remains  infectious  for  only  a 
short  time.  Among  the  measures  directed  against  yellow 
fever  are: 

First.  Quarantine.  —  While  inland  quarantine  has  never 
been  successfully  administered,  maritime  quarantine  for 
yellow  fever  is  certainly  of  value.  The  short  period  of 
incubation  of  the  disease,  the  absence  of  chronic  cases 
and  the  fact  that  it  prevails  in  endemic  form  in  only  a 
few  places  which  are  in  communication  with  the  rest  of 
the  world  chiefly  by  water,  render  it  possible  to  intercept 
at  the  port  of  debarkation  a  goodly  number  of  incom- 
ing cases.  Quarantine,  while  often  failing,  has  many  times 
proved  its  value  in  the  United  States;  and  in  Havana,  after 
the  disease  was  exterminated,  it  would  certainly  have  many 
times  been  introduced  from  Vera  Cruz  and  Colon,  and  indeed 
probably  from  New  Orleans,  if  the  careful  inspection  of 
incoming  passengers  had  not  been  maintained  by  the  depart- 
ment of  health.  The  efficiency  of  quarantine  is  greatly 
increased  if  an  agent  is  stationed  at  the  port  of  embarkation, 
as  is  done  at  many  ports  by  the  United  States  Public.  Health 
Service. 

Second.  Screefmig  of  Cases.  —  Extraordinary  effort  must 
be  made  to  get  control  of  every  case  of  the  disease.  The 
diagnosis  is  not  always  easy,  and  able  diagnosticians  must 
be  employed.  In  the  Canal  Zone  a  prize  of  $100  is  offered 
for  the  discovery  of  a  case  of  yellow  fever.  The  harsh  treat- 
ment formerly  accorded  these  cases,  the  injury  to  property 
caused  by  disinfection,  and  the  tremendous  loss  to  business 
by  the  old  methods  of  quarantine,  put  a  premium  on  con- 


INFECTION  BY  INSECTS  337 

cealment ;  but  there  is  much  less  tendency  to  hide  cases  now 
than  formerly.  When  reported,  the  case  is  protected  from 
mosquitoes  either  by  efficient  screening  or,  as  is  now  usually 
done  in  Havana  and  the  Canal  Zone,  by  removing  the  patient 
to  a  well-screened  hospital. 

Third.  Destruction  of  Mosquitoes.  —  Infected  mosquitoes 
in  the  house  occupied  by  the  patient  and  in  neighboring 
houses  must  be  destroyed.  Sulphur  dioxid  is  the  best  culi- 
cide  for  this  purpose,  but  pyrethrum  powder  may  be  burned 
while  the  room  is  occupied  and  the  stupefied  mosquitoes 
swept  up,  as  in  malaria. 

Fourth.  Prevention  of  their  Growth.  —  The  most  impor- 
tant means  of  preventing  yellow  fever  is  to  reduce  the  number 
of  stegomyia  mosquitoes  to  a  minimum  by  destroying  their 
breeding  places  in  the  same  manner  in  which  the  breeding 
places  of  malarial  mosquitoes  are  destroyed,  by  draining,  fill- 
ing, ditching  and  the  use  of  petroleum  and  culicides  in  the 
water.  As  the  stegomyia  so  often  breeds  in  domestic  recep- 
tacles which  in  the  absence  of  a  municipal  water  supply  and 
sewers  cannot  be  dispensed  with,  the  efficient  screening  of 
these  receptacles  is  an  important  part  of  sanitary  work  in 
the  American  tropics,  and  constant  inspection  is  needed  to 
see  that  the  screening  is  maintained. 

Success  of  Measures.  —  The  phenomenal  success  of  these 
measures  in  Havana  has  already  been  referred  to,  but  the 
eradication  of  the  disease  in  the  Canal  Zone  is  a  still  more 
remarkable  achievement.  Havana  is  a  compactly  built,  well- 
drained  city,  and  was  under  military  rule.  The  Canal  Zone 
is  about  forty-five  miles  long,  with  swamps  and  streams,  many 
straggling  villages  and  camps,  a  heavy  rainfall,  continuous  high 
temperature,  a  constantly  changing  non-immune  population, 
stupendous  engineering  works  altering  the  configuration  of 
the  land,  and  a  persistent  yellow-fever  infection  for  centuries. 
This  disease  had  been  the  chief  obstacle  in  the  construction 
of  the  Panama  railroad,  and  it  was  the  chief  obstacle  to  the 
French  in  their  canal  work.     Their  loss  by  death  from  this 


338       THE  SOURCES  AND  MODES  OF  INFECTION 

disease  amounted  probably  to  from  12  to  15  per  cent  per 
annum. ^  Sanitary  work  began  on  the  isthmus  in  February, 
1905,  at  which  time  yellow-fever  cases  were  being  constantly 
reported.  The  cases  soon  began  to  decrease,  and  within  a 
year  the  disease  was  practically  exterminated.^  In  Rio  Ja- 
neiro the  campaign  against  yellow  fever  began  in  April,  1903. 
The  undertaking  was  expensive,  as  it  always  must  be  if  it  is 
to  be  successful.  It  required  the  expenditure  of  $1,650,000  a 
year  and  the  employment  of  thirteen  hundred  men.  Deaths 
from  yellow  fever,  which  had  averaged  twelve  hundred  a 
year  for  nearly  forty  years,  decreased  rapidly,  as  is  shown 
by  the  following: 

Year.  Deaths. 

1903 584 

1904 48 

1905 289 

1906 42 

1907 39 

1908 4 

1909 0 

In  Vera  Cruz,  which  was  another  stronghold  of  yellow 
fever,  the  disease  has  been  almost  eradicated  by  the  employ- 
ment of  anti-mosquito  measures.^ 

Filariasis. 

First  Parasite  Studied  in  Insects.  —  While  the  infection  of 
the  blood  of  man  with  Filaria  bancrofti  is  in  most  cases  not 
accompanied  by  noticeable  symptoms,  it  is  of  interest  in  this 
connection  as  being  the  first  infection  in  which  the  parasite 
was  proved  to  be  taken  up  into  and  undergo  metamorphosis 
in  the  body  of  an  insect.     This  tiny  worm  is  found  swimming 

1  Gorgas,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  597. 

2  Cruz,  Pub.  Health  Rep.,  U.  S.  Pub.  Health  &  Mar.  Hosp.  Serv., 
Wash.,  1909,  1742. 

'  Liceaga,  Am.  Pub.  Health  Asa.  Rep.,  1905,  XXXI,  284. 


INFECTION   BY  INSECTS  339 

in  vast  numbers  in  the  blood  of  those  who  are  infected,  but 
is  found  only  at  night.  During  the  day  it  disappears  from 
the  peripheral  circulation  and  is  found  only  in  the  heart  and 
lungs.  When  these  larval  forms  are  sucked  up  by  the  mos- 
quito they  increase  rapidly  in  size  and  become  more  highly 
organized,  and  working  their  way  to  the  proboscis  of  the 
insect,  infect  the  next  person  bitten.  The  worms,  now  pre- 
senting sexual  forms,  reach  the  lymph  ducts,  where  the  eggs 
are  laid  and  whence  the  young  larvas  reach  the  blood 
current.  It  is  now  generally  beheved  that  injury  to  the 
worms  in  the  lymph  vessels  causes  obstruction  of  the  latter 
and  the  development  of  tropical  elephantiasis.  Culex  fatigans 
is  probably  the  insect  chiefly  concerned  in  the  spread  of  the 
infection.  The  disease  has  not  been  actually  transmitted  to 
man  by  the  bites  of  infected  mosquitoes,  but  the  develop- 
ment of  the  worm  in  the  mosquito  was  observed  by  Manson 
in  1878^  and  by  Lewis  in  1879.^  A  similar  infection  in  dogs 
has  been  actually  transmitted  by  means  of  mosquitoes.^ 

Sleeping  Sickness. 

Discovery  of  Trypanosome.  —  The  trypanosome  {T.  gam- 
hiensis) ,  which  is  the  cause  of  sleeping  sickness,  was  found 
in  the  blood  of  patients  by  Button  and  Todd  in  1901.  This 
disease  is  very  widely  distributed  in  Africa,  and  it  is  esti- 
mated to  have  caused  over  100,000  deaths  in  Uganda  during 
the  six  years  from  1901-1907.  This  trypanosome  is  patho- 
genic for  many  of  the  lower  animals,  and  in  monkeys  causes 
symptoms  resembling  those  produced  in  man.  Bruce  and 
Nabarro*  showed  that  the  disease  may  be  transmitted  by 
insects,  for  in  1903  they  succeeded  in  inoculating  a  monkey 
by  allowing  it  to  be  bitten  by  tsetse  flies  {Glossina  palpalis) 

»  Manson,  Med.  Times  &  Gaz.,  Lond.,  1878,  II,  731. 
2  Lewis,  Quart.  J.  Micr.  Sc,  Lond.,  1879,  XIX,  245. 
"  Braun,  The  Animal  Parasites  of  Man,  3d  ed.,  New  York,  1908,  285. 
*  Bruce  and  Nabarro,  Rep.  of  Sleeping  Sickness  Commission,  Roy. 
Soc,  1903,  No.  1. 


340       THE  SOURCES  AND   MODES  OF  INFECTION 

which  had  twenty-four  to  fort^^-eight  hours  previously  bitten 
negroes  suffering  with  the  disease.  While  this  much  has 
been  established  with  certainty,  there  are  important  points  in 
the  causation  of  the  disease  which  are  still  under  discussion. 

While  Glossina  palpalis  is  known  to  transmit  sleeping  sick- 
ness, and  the  distribution  of  this  fly  in  a  large  degree  corre- 
sponds with  the  distribution  of  the  disease,  it  is  not  certain 
whether  it  may  not  be  carried  by  other  species  of  tsetse  flies, 
and  perhaps  by  domestic  insects  and  by  mosquitoes,^  and 
Koch  ^  thinks  it  possible  that  it  may  be  transmitted  by  the 
sexual  act.  Comparatively  little  is  known  about  the  breeding 
habits  of  the  fly. 

Does  it  infect  Lower  Animals?  —  There  has  also  been  much 
discussion  as  to  whether  the  specific  trypanosome  of  this 
disease  naturally  infects  the  lower  animals.  If  they  are  gener- 
ally affected,  they  become  a  vast  reservoir  from  which  the 
trypanosomes  may  be  transferred  to  human  beings  by  the 
fly,  and  the  difficulties  in  the  way  of  controlling  the  disease 
become  enormous.  Even  the  crocodile  has  been  suggested 
by  Koch  as  an  important  "reservoir."  But  Hodges^  says 
that  actual  observation  shows  that  no  animal  except  the 
native  dog,  and  that  in  only  a  few  instances,  has  been  found 
naturally  infected.  A  cause  of  the  uncertainty  is  a  wide- 
spread distribution  of  several  kinds  of  trypanosomes  not  easily 
distinguished  from  T.  gambiensis. 

Is  it  carried  Mechanically? — Another  question  of  impor- 
tance, especially  from  a  scientific  standpoint,  is  whether  the 
trypanosome  passes  through  a  cycle  of  development  in  the 
fly.  It  was  at  first  supposed  that  this  was  the  case,  but  later 
observations,  especially  those  of  Minchin,^  seemed  to  indicate 
that  this  was  not  so.     According  to  his  observations  flies  are 

1  Bull.  Soc.  path,  exot..  Par.,  1908,  I. 

2  Koch,  Deutsche  med.  Wchnschr.,  1907,  XXXIII,  1889. 

^  Cited  in  Supl.  to  Third  Rep.,  Wellcome  Research  Lab.,  Khartoum, 
1908,  III,  172. 

*  Minchin,  Quart.  J.  Micr.  Sc,  Lond.,  1908,  n.  s.,  LII,  159. 


INFECTION  BY  INSECTS  341 

infective  at  once  after  biting  a  subject,  and  the  power  to 
infect  does  not  last  over  forty-eight  hours.  More  recently, 
however,  Bruce  ^  has  shown  that  the  parasites  do  undergo 
developmental  changes  in  the  fly,  and  that  flies  do  not  infect 
until  from  14  to  20  days  have  elapsed  after  feeding  on  a  case. 
Kleine  "  also  has  demonstrated  the  same  for  other  forms  of 
trypanosomes.  It  is  possible  that  the  trypanosomes  may  be 
occasionally  carried  mechanically  on  the  proboscis  of  the 
tsetse  fly,  in  which  case  infection  will  take  place  at  once, 
and  also  that  the  parasites  pass  through  certain  metamor- 
phoses in  the  fly,  thus  permitting  the  flies  to  remain  infective 
for  some  time. 

Prevention  of  Sleeping  Sickness.  —  The  measures  sug- 
gested for  limiting  sleeping  sickness  are: 

First.  Quarantine,  or  the  prevention  of  the  entrance  of 
infected  human  beings  into  regions  occupied  by  the  fly. 
While  this  may  be  of  value  at  times,  it  scarcely  seems  possible 
to  an  observer  at  this  distance  that  it  can  be  often  employed 
effectually  in  Africa. 

Second.  The  sick  may  be  segregated  and  kept  out  of 
reach  of  the  flies  until  the  trypanosomes  have  disappeared 
from  the  blood. 

Third.  The  removal  of  the  entire  population  from  the 
area  occupied  by  the  fly.  The  tsetse  flies  are  found  only  from 
thirty  to  one  hundred  yards  from  water,  so  that  if  all  settle- 
ments are  removed  this  distance  from  rivers  and  lakes  much 
will  be  done  to  prevent  the  spread  of  the  disease. 

Fourth.  As  trees  and  shrubs  afford  a  hiding  place  for  the 
flies,  the  thorough  clearing  of  the  land  around  villages  and 
near  landing  places  and  shore  market  places  has  been  found 
useful,  just  as  similar  clearing  has  been  found  to  be  an  impor- 
tant means  of  controlling  malaria  in  the  Canal  Zone  at 
Panama. 

1  Bruce,  Bull,  of  Sleeping  Sickness  Bu.,  1909,  Nos.  6  &  7. 
*  Kleine,  Deutsche  med.  Wchnschr.,  1909,  XXXV,  924. 


342       THE  SOURCES  AND  MODES  OF  INFECTION 

Fifth.  The  administration  of  atoxyl  (anilin  meta-arse- 
nate)  is  believed  by  many  to  shorten  the  life  of  the  parasite 
in  the  body,  and  if  so,  it  becomes  a  valuable  prophylactic 
measure,  similar  to  the  use  of  quinia  in  malarial  affections. 

Kala-azar. 

Protozoan  Discovered  by  Leishman.  —  Kala-azar,  or  dum- 
dum fever,  occurs  in  various  tropical  countries,  particularly 
in  India.  It  runs  a  chronic  course  and  is  characterized  by 
marked  enlargement  of  the  spleen.  In  1900  Leishman  dis- 
covered in  splenic  pulp,  from  a  case  of  the  disease,  certain 
bodies  the  importance  of  which  he  did  not  appreciate,  but 
later,  in  1903,  he  concluded  that  they  might  be  protozoa. 
The  discovery  was  confirmed  the  same  year  by  Donovan. 
These  bodies  are  now  recognized  as  protozoa,  and  are  known 
as  Leishmania  donovani,  and  are  probably  the  cause  of  the 
disease.  Similar  bodies  were  found  by  Wright  of  Boston  in 
oriental  sore,  and  by  Nicolle  and  Cassuto  in  an  infantile 
splenic  disease  in  Tunis.  Rogers,  Patton  and  others  have 
succeeded  in  growing  the  parasite  in  culture  medium  outside 
of  the  body,  and  both  have  also  obtained  evidence  to  show 
that  the  disease  may  be  transmitted  by  the  bedbug.  Both 
Patton  and  Rogers  have  shown  that  a  well-defined  cycle  of 
development  takes  place  in  the  body  of  that  insect,  which 
renders  it  very  probable  that  it  is  the  intermediate  host. 
Patton  says,  "There  is  no  shadow  of  doubt  that  the  bed- 
bug transmits  the  disease,"  but  this  has  as  yet  not  been 
definitely  proved.^ 

Dengue. 

Transmitted  by  Mosquitoes.  —  The  causation  and  mode 
of  transmission  of  dengue  are  somewhat  uncertain.  Graham 
believes  that  he  has  demonstrated  in  the  blood  a  protozoan 

*  The  above  is  taken  chiefly  from  The  Malarial  Fevers,  Craig,  1909, 
411,  and  the  Supplement  to  the  Third  Report  of  the  Wellcome  Research 
Laboratories,  1908,  95. 


INFECTION  BY  INSECTS  343 

which  he  considers  the  cause  of  the  disease,  but  his  findings 
have  not  been  substantiated.  Ashburn  and  Craig  ^  demon- 
strated that  it  is  possible  to  transfer  the  disease  to  healthy- 
men  by  the  inoculation  of  blood  from  the  sick,  and  that  the 
virus  is  contained  in  the  filtered  blood.  They  also  proved 
that  the  disease  can  be  transmitted  by  a  mosquito,  Culex 
fatigans,  and  they  consider  that  this  is  probably  the  most 
common  mode  of  transmission.  Stitt  also  believes  that  the 
mosquito  is  the  bearer  of  the  disease.  Carpenter  and  Sut- 
ton could  not  transfer  the  disease  by  mosquitoes,  but  they 
did  not  experiment  with  C.  fatigans.  Ross  has  shown  that 
while  dengue  prevailed  elsewhere  in  Egypt,  there  was  none 
in  Port  Said  and  Ismailia,  where  the  mosquitoes  had  been 
exterminated.  Balfour,-  from  whose  review  this  information 
is  chiefly  taken,  states  that  in  Khartoum,  which  was  com- 
paratively free  from  mosquitoes,  especially  C.  fatigans,  there 
was  no  dengue,  though  persons  with  the  disease  in  all  proba- 
bility came  there  from  Port  Sudan  and  Haifa.  It  appears 
probable,  therefore,  that  the  contentions  of  Ashburn  and 
Craig  are  correct. 

Relapsing  Fever. 

Varieties.  —  According  to  Craig,^  there  are  at  least  four 
forms  of  relapsing  fever,  each  due  to  a  particular  kind  of 
spirocheta,  and  each  apparently  limited  in  geographical  dis- 
tribution. It  is  still  uncertain  whether  these  spirochetae  are 
bacteria,  as  was  formerly  believed  and  as  is  strongly  urged 
by  Novy  and  Knapp,  or  protozoa,  similar  to  the  trypano- 
somes,  as  is  maintained  by  Schaudinn,  Prowazek,  Leishman 
and  others.  Whatever  they  may  be,  there  is  no  doubt  that 
at  least  one  form  of  the  disease  is  carried  from  person  to 
person  by  means  of  ticks. 

'  Ashburn  and  Craig,  J.  Infect.  Dig.,  Chicago,  1907,  IV,  440;  also 
Philippine  J.  So.  [B.  Med.],  II,  93. 

^  Supplement  to  the  Third  Rep.,  Wellcome  Research  Lab.,  Khar- 
toum, 1908,  37. 

»  Craig,  The  Malarial  Fevers,  New  York,  1909,  445. 


344       THE  SOURCES  AND  MODES  OF  INFECTION 

Ticks.  —  The  African  form  of  relapsing  or  tick  fever  is 
caused  by  S.  duttoni,  which  was  discovered  by  Dutton  and 
Todd,  and  also  by  Ross  and  Milne  in  1904,  the  first  named 
of  whom,  Dutton,  lost  his  life  while  studying  the  disease. 
Dutton  and  Todd  demonstrated  beyond  question  that  the 
disease  may  be  carried  from  man  to  man  by  a  tick,  Ornitho- 
dorus  mouhaia,  and  their  observations  were  confirmed  by  Ross 
and  Milne  and  by  Breinl  and  Kinghorn.  It  was  also  shown 
that  the  disease  is  hereditary  in  ticks,  according  to  Mollers,* 
even  to  the  second  generation.  Unlike  the  malarial  parasites 
and  the  trypanosomes,  these  spirochetse  soon  disappear  from 
the  blood,  and  chronic  latent  infections  do  not  seem  to  exist. 
Koch,  however,  suggests  that  the  spirochetse  may  ultimately 
be  found  in  rats,  and  that  these  rodents  may  be  the  real 
source  of  this  disease,  as  they  are  of  plague.  The  tick,  how- 
ever, is  said  to  be  exclusively  a  human  parasite.  It  is  found 
in  the  floors  and  crevices  of  houses  and  native  huts,  where  it 
hides  during  the  day  and  feeds  at  night.  The  spirochetse 
undergo  a  certain  development  and  multiplication  in  the  tick, 
but  whether  they  pass  through  a  definite  cycle  of  develop- 
ment, like  the  protozoa,  is  not  known.  Ticks  have  been 
known  to  be  infective  for  a  year  and  a  half. 

Bedbugs.  —  Even  before  the  discovery  of  the  spirocheta  it 
was  suggested  that  the  bedbug  might  be  the  carrier  of  the  dis- 
ease, but,  according  to  Balfour,^  Breinl  and  Kinghorn,  and 
Todd  have  by  experiment  shown  that  this  is  probably  not  so. 

Less  is  known  about  the  other  forms  of  relapsing  fever. 
Tictin  in  1897  believed  that  the  recurrent  fever  of  Europe  is 
transmitted  by  the  bedbug,  and  he  claimed  to  have  demon- 
strated its  possible  transmission  in  this  way,  but  the  experi- 
ments were  not  entirely  satisfactory  and  have  not  been 
substantiated. 

*  Mollers,  Ztschr.  f.  Hyg.  u.  Infectionskrankh.,  Leipz.,  1908,  LVIII, 
277. 

^  Supplement  to  the  Third  Report,  Wellcome  Research  Lab., 
Khartoum,  1908,  190. 


INFECTION  BY  INSECTS  345 

The  Indian  form  of  the  disease  is  caused  by  S.  carteri,  and 
has  been  much  studied.  Mackie  could  demonstrate  the  spi- 
rochetae  in  bedbugs  fed  on  relapsing-fever  patients,  up  to 
the  sixth  day,  but  he  found  no  evidence  of  their  increase. 
Of  fifty-three  bugs  found  in  a  fever  ward,  only  one  contained 
spirochetae.  He  also  placed  infected  bedbugs  in  cages  with 
six  monkeys,  and  only  one  of  the  monkeys  contracted  the 
disease.      Other  sources  could  not  be  excluded. 

Lice.  —  Recently  the  same  author  has  found  the  spiro- 
chetae in  from  two  to  fourteen  per  cent  of  body  lice  found  in 
fever  wards,  and  he  showed  that  the  parasites  increased 
in  number  in  the  lice.  Sergent  and  Foley,  in  Algeria,  have 
made  observations  and  experiments  tending  to  implicate  the 
clothes  louse,  Pediculus  vestimenti. 

Rocky  Mountain  Fever. 

Transmitted  by  Ticks.  —  Rocky  Mountain  tick  fever  prob- 
ably appeared  in  Idaho  about  1885,  and  is  now  found  in 
Idaho,  Montana,  Washington,  Oregon,  Wyoming  and  Utah. 
It  is  an  acute  fibrile  disease  with  a  high  mortality,  usually 
exhibits  an  eruption  on  the  skin,  and  is  followed  by  immunity. 
According  to  the  investigations  of  Ricketts,^  the  disease  is 
transmitted  by  means  of  ticks,  probably  from  some  of  the 
small  wild  animals  of  the  country.  He  showed  that  it  is 
possible  to  transmit  the  disease  to  monkej^s,  guinea  pigs, 
gophers,  chipmunks,  rock  squirrels  and  other  animals  by 
allowing  ticks  (Dermacenter  andersoni)  to  bite  first  an  infected 
animal,  and  later  a  healthy  animal,  which  soon  becomes 
infected.  There  is  evidence  that  the  virus  of  the  disease 
develops  in  the  body  of  the  tick  and  is  transmitted  to  its 
offspring.  Ricketts  has  shown  by  inoculation  experiments 
that  the  virus  is  contained  in  the  blood  serum  of  infected 
animals,  and  he  recently^  reports  the  discovery  of  a  bacillus 
which  he  believes  to  be  the  cause  of  the  disease. 

»  Ricketts,  Rep.  St.  Bd.  Health,  Idaho,  1907-08,  88. 
2  Ricketts,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  379. 


346       THE  SOURCES  AND  MODES  OF  INFECTION 

Biological  Carriers  Distinguished  from  Mechanical  Carriers. 

— In  most  of  the  diseases  thus  far  considered  in  this  chapter 
the  parasite  which  causes  the  disease  passes  through  a  defi- 
nite cycle  of  its  existence  in  the  insect  as  well  as  in  man. 
The  insect  is  in  most  cases  the  true  host  of  the  parasite  and 
has  been  called  a  "  biological  carrier  "  of  disease.  Most  of 
the  parasites  transmitted  in  this  way  belong  to  the  protozoa. 
On  the  other  hand,  insects  may  be  merely  "  mechanical 
carriers  "  of  disease.  The  blood  which  contains  the  germs  of 
the  disease  may  be  carried  on  the  mouth  parts  of  the  insect 
and  inoculated  into  the  next  person  bitten,  just  as  it  might 
be  carried  on  the  point  of  a  lancet. 

Plague. 

Discovery  of  Bacilli  in  Fleas.  —  According  to  Nuttall/ 
Ogata  in  1897  found  plague  bacilli  in  fleas  taken  from  the 
body  of  a  rat  dead  of  bubonic  plague,  and  this  observation 
was  confirmed  by  the  German  Plague  Commission  the  same 
year.  In  1898  Simond  noted  that  persons  who  handle  dead 
rats  not  rarely  die  of  the  plague,  but  he  found  that  infection 
never  occurred  if  the  rats  had  been  dead  over  twenty-four 
hours.  He  also  found  that  persons  with  plague  occasionally 
presented  on  their  skin  what  appeared  to  be  flea  bites,  and 
he  was  able  to  demonstrate  plague  bacilli  in  these  supposed 
bites.  He  was  able  also  to  demonstrate  plague  bacilli  in 
fleas  taken  from  rats  dead  of  the  plague. 

Plague  derived  from  Rodents.  —  Simond's  observations 
led  to  much  study  and  experiment  and  to  still  more  contro- 
versy. It  has  been  shown  by  large  numbers  of  observations 
that  plague  is  primarily  a  disease  of  the  lower  animals,  par- 
ticularly of  rodents,  many  species  'of  which  easily  become 
infected.  It  has  been  shown  also  that  plague  in  man  is  gen- 
erally derived  from  the  same  disease  in  rats,  or  more  rarely 
mice,  and  recently  in  California  from  ground  squirrels  {CiteU 
lus  beecheyi). 

1  Nuttall,  Johns  Hopkins  Hosp.  Rep.,  Bait.,  1899,  VIII,  1. 


INFECTION  BY  INSECTS  347 

Epidemiological  Evidence.  —  The  very  careful  observa- 
tions of  Thompson  1  in  Austraha  showed  that  outbreaks  of 
human  plague  were  preceded  by  outbreaks  of  rat  plague, 
that  human  cases  were  connected  in  one  way  or  another  with 
foci  of  rat  infection,  and  that  the  dispersal  of  human  cases 
did  not  result  in  the  dispersion  of  plague.  He  showed  that 
while  human  plague  had  a  local  association  with  rat  plague, 
the  association  was  not  a  direct  one,  but  was  such  as  to  render 
necessary  the  assumption  of  some  such  intermediary  as  the 
flea.  It  also  seemed  to  him  that  the  location  of  the  buboes 
was  in  accord  with  the  theory  of  flea  infection. 

Experimental  Work.  —  Objection  had  been  made  by  Nut- 
tall  and  others  to  the  flea  theory  on  the  ground  that  rat  and 
human  fleas  are  of  different  species,  but  Tidswell  in  Sydney^ 
showed  that  rat  fleas  when  hungry  will  bite  man.  This  has 
been  substantiated  b}^  many  other  observers,  some  of  whom 
have  also  shown  that  Pulex  irritans,  the  human  parasite,  will 
occasionally  bite  rats.  It  has  also  been  shown  that  fleas 
speedily  leave  a  dead  animal,  and  then,  impelled  by  hunger, 
they  attack  the  nearest  victim.  As  was  shown  by  Nuttall, 
plague  bacilli  may  live  in  fleas  for  several  days.  The  English 
Plague  Commission  found  as  many  as  5000  bacilli  in  the 
stomach  of  a  single  flea,  and  they  beheve  that  they  increase 
in  number  for  a  while  and  sometimes  live  for  fifteen  days, 
but  in  starved  fleas  do  not  live  over  a  week.^  Verjbitski  *  has 
also  confirmed  these  observations.  He  has  shown,  too,  as  did 
Nuttall,  that  bedbugs  may  become  infected  and  harbor  the 
germs  for  some  da3's.  According  to  Tidswell,^  rats  are  fre- 
quently infested  with  bedbugs  (Cimex  lectularius) ,  but  there 
is  no  evidence  as  yet  that  these  play  any  important  part  in 

1  Thompson,  Reports  of  Plague  in  Sydney,  1902  to  1907. 
'  Tidswell,  Rep.  on  Second  Outbreak  of  Plague  in  Sydney,  1902, 
73-75. 

'  J.  Hyg  ,  Cambridge,  1907,  VII,  419. 

•  Verjbitski,  J.  Hyg.,  Cambridge,  1908,  VIII,  162. 

*  Loc.  cit. 


348       THE  SOURCES  AND  MODES  OF  INFECTION 

the  causation  of  the  disease.  Verjbitski  showed  that  if  the 
biting  insect  is  crushed  on  the  skin,  either  the  bite  or  neigh- 
boring scratches  are  easily  infected. 

Demonstrations  in  India.  —  Finally,  the  very  beautiful 
experiments  of  the  English  Plague  Commission^  showed  con- 
clusively that  infection  by  fleas  was  practically  the  only  way 
in  which  experimental  animals  could  be  infected  under  natural 
conditions.  These  experiments  have  been  referred  to  on 
pages  204  and  262.  In  one  experiment,  a  plague-infected  vil- 
lage was  cleared  of  its  human  inhabitants  and  guinea  pigs 
placed  in  the  houses,  and  it  was  demonstrated  that  infection 
took  place  only  through  the  medium  of  fleas.  The  experi- 
mental and  epidemiological  evidence  is  that  the  bubonic  form 
of  human  plague,  which  is  by  far  the  most  common  form,  is 
caused  by  the  transference  of  the  bacilli  from  rodents  to  man 
by  means  of  fleas. 

Plague  rarely  spread  except  by  Fleas.  —  While  it  is  true 
that  the  flea  is  the  chief  agent  in  the  transmission  of  plague, 
the  disease  may  possibly  be,  and  doubtless  occasionally  is, 
spread  in  other  ways.  In  experimental  animals  it  is  possible 
to  induce  it  by  the  ingestion  of  infected  food,  and  the  contact 
of  the  abraded  or  injured  skin  with  any  substance  containing 
plague  bacilli  may  result  in  infection.  The  pneumonic  form 
of  plague,  when  no  precautions  are  taken,  is  highly  contagious, 
for  the  sputum  contains  the  bacilli.  In  some  outbreaks  of 
plague  the  pneumonic  form  prevails.  In  some  localities  the 
overcrowding,  filth  and  habits  of  the  people  may  cause  con- 
tact infection  or  infection  by  food  to  assume  some  impor- 
tance, but  in  Western  Europe,  Australia  and  America  there 
can  be  little  doubt  that  plague  is  chiefly  a  flea-borne  disease. 

Measures  against  Plague.  —  Measures  against  the  plague 
ought,  then,  to  involve  the  isolation  of  the  sick,  particularly 
those  sick  with  the  pneumonic  form.     In  India  evacuation 

.    ^  J.  Hyg.,  Cambridge,  1906,  VI. 

See  also  Summary  of  Work  of  Commission,  1908,  Calcutta,  Supt.  of 
Gov.  Printing. 


INFECTION  BY  INSECTS  349 

of  infected  villages,  that  is,  the  removal  of  the  population 
from  the  vicinage  of  the  plague  rat,  is  a  measure  of  value. 
Disinfection,  if  it  includes  the  killing  of  fleas  and  rats,  is  an 
important  measure.  Haffkine's  serum  has  been  found  to  pre- 
vent attacks  for  several  months,  and  its  general  use  is  often 
of  value  in  preventing  the  development  of  individual  cases. 
But  the  chief  anti-plague  measures  must  be  directed,  not 
against  the  flea,  but  against  rats  and  other  rodents.  The  most 
obvious  procedure  is  to  attempt  the  destruction  of  the  rats, 
but  thus  far  this  has  proved  to  be  a  rather  hopeless  under- 
taking. Poisoning,  trapping  and  destruction  by  infectious 
disease  have  proved  only  palliative  or  adjuvant  measures. 
In  Japan,  in  Australia  and  in  California  the  most  energetic 
rat  destruction  has  not  materially  reduced  their  numbers. 
Thompson  ^  says :  "Prevention  of  epidemic  plague  conse- 
quently lies  in  maintaining  a  distance  between  the  rat  and 
man.  The  requisite  separation  between  rat  and  man  will  be 
better  secured  by  improving  the  construction  of  buildings 
than  by  attempts  to  exterminate  the  rat."  In  Sydney  large 
sums  are  being  spent  in  rebuilding  wharves  and  warehouses 
so  as  to  render  them  rat-proof.  In  San  Franscisco  ^  every 
effort  has  been  made  to  prevent  the  growth  of  rats  by  cutting 
off  their  food  supply,  by  improved  scavenging,  and  by  pro- 
viding metal  garbage  pails  and  rat-proof  receptacles  for  all 
kinds  of  food  and  grain  likely  to  attract  rats.  But  the  chief 
effort  was  directed  to  rat-proofing,  by  the  use  of  concrete 
construction,  of  stables,  markets,  provision  and  produce  ware- 
houses and  wharves. 

Anthrax. 

Nuttall,  in  his  valuable  discussion  and  bibliography  of  the 
subject  of  insect  carriers  of  disease,^  cites  a  large  number  of 

1  Thompson,  Internat.  Cong.  f.  Hyg.  u.  Demog.,  Berl.,  1907,  III,  672. 

*  Eradicating  Plague  from  San  Francisco,  Rep.  of  Citizens'  Health 
Com.,  1909. 

»  Nuttall,  Johns  Hopkins  Hosp.  Rep.,  Bait.,  1S99,  VHI,  1;  see  also 
Rep.  to  Local  Gov.  Bd.,  Lond.,  on  Pub.  Health,  1909,  n.  s.,  16. 


350       THE  SOURCES  AND  MODES  OF  INFECTION 

authors  who  suggest  that  anthrax  may  at  times  be  trans- 
mitted by  any  biting  insects  which  pass  from  cattle  to  man. 
Numerous  instances  are  given  of  persons  who  date  the  begin- 
ning of  their  pustule  from  the  sharp  sting  of  an  insect,  but, 
as  was  well  said,  it  is  probable  that  often  the  first  noticeable 
sensations  in  the  development  of  the  pustule  are  wrongly 
considered  as  due  to  the  bite  of  an  insect.  In  a  few  cases  a 
fly  was  felt  to  bite  and  was  killed,  and  on  the  spot  a  ma- 
lignant pustule  developed.  Most  of  the  score  or  more  of 
writers  quoted  urge  this  mode  of  infection  on  purely  a  priori 
grounds,  and  it  is  certainly  highly  probable  that  where 
anthrax  is  at  all  prevalent  among  animals,  and  biting  insects 
pass  from  the  lower  animals  to  human  beings,  the  disease  is 
sometimes  transmitted  in  this  way;  but,  as  has  been  sug- 
gested, if  this  happened  often,  the  disease  would  be  more 
common  than  it  is.  Certainly  in  England  and  the  United 
States  practically  all  human  anthrax  results  from  handling 
infected  material. 

Nuttall '  allowed  bedbugs  to  suck  blood  from  mice  infected 
with  anthrax,  and  then  caused  them  immediately  to  bite 
healthy  mice.  In  all,  136  infected  bugs  were  used,  but  in  no 
instance  did  they  transmit  the  disease.  In  six  instances  the 
bugs  were  crushed  while  biting,  but  these  experiments  were, 
like  the  others,  without  result.  Nuttall  also  made  a  few 
similar  experiments  with  fleas,  with  like  negative  results.  He 
found  that  anthrax  bacilli  remained  alive  in  bedbugs  only 
for  from  two  to  four  days,  and  died  off  even  more  quickly 
in  fleas. 

Nuttall  carried  on  similar  experiments  with  bedbugs  and 
chicken  cholera,  but  these  were  equally  unsuccessful. 

Septic  Infection. 

Nuttall  cites  Faure,  Paltauf,  Chrzaszczewski,  Joseph  and 
Berry  as  having  noted  instances  of  septic  infection  following 
the  bites  of  insects,  and  others  are  occasionally  noted  in  medi- 
*  Nuttall,  loc.  cit.,  13. 


INFECTION  BY  INSECTS  351 

cal  literature.     That  this  accident  should  sometimes  happen 
seems  very  probable. 

Typhoid  Fever. 

Dutton  ^  caused  bedbugs  to  bite  a  typhoid-fever  patient 
and  after  twenty-four  hours'  fasting  to  bite  two  other  healthy 
persons,  both  of  whom  developed  typhoid  fever  in  twelve 
and  fourteen  days  respectively. 

Insects  carry  Germs  on  Bodies.  —  The  insects  thus  far 
considered  inoculate  disease  by  means  of  their  bites,  but  it  is 
evident  that  some  diseases  may  be  carried  by  them  in  other 
ways.  If  infective  material  exists  in  considerable  quantity, 
and  is  accessible  to  insects,  they  are  almost  certain  to  get  it 
on  their  legs  and  bodies,  and  may  then  carry  the  germs  to 
other  human  beings.  The  chance  of  their  doing  this  varies 
greatly  with  varying  conditions.  If  the  insects  fly,  the  danger 
would  seem  to  be  much  greater..  If  the  infective  material  is 
large  in  amount  and  freely  exposed,  as  typhoid  excreta  in 
privy  vaults,  the  danger  of  fly  infection  is  increased,  and  it 
is  also  greater  if  there  is  a  possibility  of  infecting  food  which 
insects  love  to  visit. 

Flies  carry  Germs.  —  It  is  therefore  not  surprising  that 
many  persons,  even  years  ago,  suggested  that  insects  might 
be  the  carriers  of  disease.  Nuttall  cites  many  of  these. 
With  the  development  of  bacteriology,  experiments  began  to 
supplement  conjecture,  and  it  was  definitely  determined  that 
bacteria  might  be  carried  on  the  bodies  of  insects,  which 
indeed  is  self-evident,  and  also  that  they  might  in  a  living 
state  pass  through  the  stomach  and  be  voided  in  the  feces. 
According  to  Nuttall,  Raimbert,  Davaine  and  Ballinger 
demonstrated  living  anthrax  bacilli  on  flies  of  various  kinds 
that  had  been  feeding  on  infected  material.  Nuttall  himself 
showed  that  house  flies  could  carry  for  forty-eight  hours 
living  plague  bacilli  which  they  had  derived  from  material 
they  had  fed  on,  and  Hankin  showed  the  same  for  ants. 
1  Dutton,  J.  Am.  M.  Ass.,  Chicago,  1909,  LIII,  1248. 


352       THE  SOURCES  AND  MODES  OF  INFECTION 

Cholera.  —  In  ]  886  Tizzoni  and  Cattani  caught  flies  in  a 
cholera  hospital  in  Bologna  and  found  that  cultures  made 
from  them  showed  cholera  spirilla.  Simmonds  made  similar 
observations  in  Hamburg  in  1892.  Macrae  in  India,  in  1894, 
exposed  boiled  milk  in  different  parts  of  a  jail  where  cholera 
prevailed,  and  found  that  it  became  infected  with  cholera 
germs.  Tsuzki,  in  1904,  captured  cholera-infected  flies  in  a 
house  in  Tientsin  where  there  were  cases  of  the  disease. 
Chantemesse  and  Gagnon  have  shown  that  flies  may  carry- 
virulent  germs  for  seventeen  and  twenty-four  hours  re- 
spectively. Maus  ^  says  that  cholera  spirilla  were  found  on 
several  bluebottle  flies  caught  in  infected  houses  in  the 
Philippines. 

Tjrphoid  Fever.  —  Celli  fed  flies  with  pure  cultures  of 
the  typhoid  bacillus  and  found  that  virulent  germs  passed 
through  the  intestines.  Firth  and  Horrocks^  showed  that 
typhoid  bacilli  could  be  carried  on  the  legs  and  bodies  of 
flies,  but  they  did  not  prove  that  they  could  pass  through  the 
digestive  tract  of  the  insects.  Hamilton  ^  in  Chicago,  and 
Fricker  in  Hamburg,  in  the  same  year,  recovered  typhoid 
bacilli  from  flies  in  houses  where  there  were  cases  of  the 
disease.  Klein  *  also  recovered  typhoid  bacilli  from  flies  from 
houses  where  there  was  typhoid  fever.  Buchanan^  did  not 
find  typhoid  bacilli  on  flies  caught  in  an  enteric-fever  ward, 
but  he  found  that  flies  could  readily  be  made  to  distribute 
typhoid  germs  over  an  agar  plate.  Prof.  F.  P.  Gorham,  at 
my  request,  exposed  agar  plates  in  the  pantry  of  a  house 
where  there  were  five  cases  of  typhoid  fever.  The  place  was 
swarming  with  flies  and  the  privy  was  just  outside  of  the 
window.  Flies  were  frequently  walking  over  the  plates,  but 
no  typhoid  bacilU  were  found.     Gunn,  in  Orange,  N.  J.,  was 

»  Maus,  Abst.  Med.  News,  N.  Y.,  1902,  LXXXI,  318. 
2  Firth  and  Horrocks,  Brit.  M.  J.,  Lond.,  1902,  II,  936. 
8  Hamilton,  J.  Am.  M.  Ass.,  Chicago,  1903,  XL,  576. 
4  Klein,  Brit.  M.  J.,  Lond.,  1908,  II,  1150. 
6  Buchanan,  Abst.,  Glasgow  M,  J.,  1907,  LXVII,  305. 


INFECTION  BY  INSECTS  353 

similarly  unsuccessful.  Hewitt  ^  allowed  flies  to  walk  over 
thin  smears  of  tj^phoid  feces  and  then  kept  them  in  cages 
for  24  hours  and  after  that  allowed  them  to  walk  over 
culture  media.  No  typhoid  colonies  were  found  but  only  a 
few  of  B.  coll.  Similar  experiments  were  made  with  B. 
prodigiosus  with  negative  results,  though  the  germs  were 
recovered  from  the  feet  of  the  flies  after  12  hours.^ 

Dysentery.  —  Auche  ^  allowed  flies  to  become  contami- 
nated with  cultures  of  the  dysentery  bacillus,  and  found  that 
they  could  carry  the  germs  for  hours,  and  that  the  flies  would 
take  up  the  bacilli  from  feces  as  well  as  from  cultures. 

Tuberculosis.  —  Spillmann  and  Haushalter  found  tubercle 
bacilli  in  the  intestines  and  in  the  dejecta  of  flies  that  had 
fed  on  tuberculous  sputum.  Hoffmann  found  tubercle  bacilli 
in  four  of  six  flies  captured  in  a  room  occupied  by  a  tuber- 
culous patient,  and  also  in  the  excreta  of  flies  scraped  from 
the  walls  and  furniture  of  the  room.  Lord  *  found  virulent 
bacilli  in  flyspecks,  but  could  not  induce  the  disease  by  caus- 
ing guinea  pigs  to  breathe  air  drawn  over  infected  specks. 
Hayward^  demonstrated  living  bacilli  in  flyspecks  after  the 
flies  had  been  fed  on  sputum  in  such  a  way  as  to  preclude 
the  possibility  of  the  infection  of  their  feet  or  bodies.  Andre  ' 
demonstrated  tubercle  bacilli  in  the  excreta  of  flies  b\'  inocu- 
lation tests,  and  he  found  that  they  appeared  in  the  feces 
about  six  hours  after  feeding  and  continued  for  five  days. 
Flies  may  also  become  infected  by  eating  tuberculous  dust. 

Numerous  experiments  have  been  made  with  various  sapro- 
phytic bacteria  to  prove  that  they  may  be  readily  carried  by 
insects.  A  common  show  experiment  of  the  laboratory  or 
of  "  health  exhibitions  "  is  to  allow  some  insect,  as  a  fly  or 

1  Hewitt,  Quart.  J.  Micr.  Sc,  1909,  n.  s.,  LIV,  394. 

2  Ibid.,  403. 

8  Auche,  Compt.  rend.,  Soc.  de  biol.,  Par.,  1906,  LXI,  450. 

*  Lord,  Boston  M.  &  S.  J.,  1904,  CLI,  651. 

'  Hay  ward,  N.  York  M.  J.  [etc.],  1904,  LXXX,  643. 

"  Andre,  6th  Internat.  Cong,  on  Tuberc,  Wash.,  1908,  I,  162. 


354       THE  SOURCES  AND   MODES  OF  INFECTION 

cockroach,  to  walk  across  an  agar  plate  leaving  rows  of  bac- 
terial colonies  to  mark  its  footprints.  In  1899  the  writer, 
with  the  assistance  of  Prof.  F,  P.  Gorham,  exposed  agar 
plates  and  dishes  of  milk  in  the  pantry  of  a  house,  and  poured 
large  amounts  of  a  culture  of  B.  prodigiosus  into  the  near-by 
privy  vault.  Of  nine  tests,  four  showed  infection  with  pro- 
digiosus, while  all  of  five  plates  exposed  near  the  vault  were 
so  infected.  Plates  covered  with  wire  netting  were  not 
infected.  Flies  were  very  numerous  and  were  constantly 
walking  over  the  plates. 

Wild  Flies  carry  Fecal  Bacteria.  —  Flies  caught  in  the 
open  have  been  shown  to  be  at  times  loaded  with  fecal  bac- 
teria, thus  indicating  at  once  their  habits  and  the  possibility 
of  their  carrying  certain  diseases.  Jackson^  found  as  many 
as  100,000  fecal  bacteria  on  a  single  fly,  and  as  a  general 
thing  the  nearer  the  flies  were  to  the  sewer  outlets  the  more 
numerous  were  this  class  of  bacteria.  Graham-Smith^  found 
fecal  bacteria  on  23.6  per  cent  of  148  flies  examined  in  Cam- 
bridge, England.  For  a  part  of  them  the  surface  of  the  body 
only  was  examined,  and  for  a  part  the  intestine  only.  Sur- 
face infection  was  about  two  and  a  half  times  as  frequent  as 
intestinal  infection.  The  highest  degree  of  infection  was 
found  among  flies  caught  near  decaying  animal  matter,  and 
next  among  those  caught  near  manure.  Nash  ^  recovered 
B.  coli  from  a  fly  caught  in  a  hospital  ward.  Delepine  * 
found  bacilli  of  the  colon  type  in  four  of  thirty-five  collections 
of  flies  caught  in  Manchester. 

Flies  in  Spanish  War.  —  That  flies  are  capable  of  carrying 
bacteria  from  privy  vaults  to  food  indoors,  is  indicated  by 
the  observations  of  Gorham  noted  above.     Vaughan  ^  also 

1  Jackson,  Rep.  to  Com.  on  Pollution  [etc.],  of  the  Merchants'  Ass.  of 
N.  York,  1907,  16. 

2  Graham-Smith,  Further  Preliminary  Rep.  on  Flies  [etc.],  Rep.  to 
Loc.  Gov.  Bd.  on  Health,  n.  s.,  1909,  16. 

3  Nash,  J.  Hyg.,  Cambridge,  1909,  IX,  141. 

4  Delepine,  Rep.  on  Health  of  Manchester,  1906,  85. 
6  Vaughan,  J.  Am.  M.  Ass.,  1900,  XXXIV,  1456. 


INFECTION  BY  INSECTS  355 

reports  that  during  the  Spanish  War  flies  covered  with  a 
white  coating  of  Hme  were  often  seen  crawhng  over  the  food, 
the  lime  showing  that  they  had  just  come  from  the  latrines 
where  lime  had  been  thrown  over  the  fecal  matter. 

Species  of  Flies.  —  Flies  more  often  than  any  other  insect 
have  been  accused  of  thus  carrying  disease  germs.  Of  these 
by  far  the  most  common  in  dwellings  is  the  housefly,  Musca 
domestica,  though  other  flies  are  not  infrequently  found.  In 
New  York  Jackson  found  that  98  per  cent  of  all  flies  captured 
were  M.  domestica.  In  London  in  1908  Austen^  found  that 
next  to  the  house  fly  the  most  common  species  were  Homa- 
lomyia  canicularis,  Calliphora  erythrocephala  and  Muscina 
stabulans.  In  Providence  in  1909  Sykes "  found  all  the  above, 
and  also  considerable  numbers  of  Lucilia  coesar,  Sarcophaga 

?  and  Stomoxys  calcitrans,  and  a  few  Sce?iopinus  fen- 

estralis,  but  99  per  cent  of  the  flies  caught  indoors  were 
M.  domestica.  The  bluebottle  fly,  Lucilia  coesar,  has  been 
accused  by  Button^  of  transmitting  typhoid  fever.  Maus 
in  the  Philippines  blames  bluebottles  for  the  spread  of 
cholera. 

Mayer  *  states  that  some  ants  were  seen  to  pass  between 
cages  containing  mice,  some  of  which  were  sick  with  mouse 
typhoid  and  some  well.  The  well  mice  soon  developed  the 
disease,  and  agar  plates  so  placed  that  the  ants  ran  over 
them  showed  numerous  colonies  of  the  B.  murium  typhi. 

Cockroaches  and  Other  Insects.  —  Engelmann  ^  reports 
cockroaches  extremely  numerous  in  certain  houses  in  Chicago 
where  typhoid  fever  prevailed,  and  she  attributed  the  spread 
of  the  disease  to  these  insects.  Weber*  accuses  various  species 
of  Psocidoe  of  carrying  tubercle  bacilli  from  cow  to  cow,  and 

'  Austen,  Rep.  to  Local  Gov.  Bd.  on  Pub.  Health,  n.  s.,  1909,  No.  5. 

2  Sykes,  Rep.  Supt.  of  Health,  Providence,  1909,  13. 

'  Button,  J.  Am.  M.  Ass.,  Chicago,  1909,  LHI,  1561. 

*  Mayer,  Miinchen  med.  Wchnschr.,  1905,  LH,  226. 

5  Engelmann,  Med.  News,  N.  Y.,  1903,  LXXXII,  225. 

«  Weber,  N.  York  M.  J.  [etc.],  1906,  LXXXIV,  884. 


356       THE  SOURCES  AND  MODES  OF  INFECTION 

states  that  he  demonstrated  the  germs  in  one  of  these  insects 
found  in  a  manger.  In  fact  any  "  domestic  "  insect  with 
power  of  active  locomotion,  and  of  filthy  habits,  may  be  con- 
sidered as  a  possible  carrier  of  disease  germs.  But  the  house 
fly  is  undoubtedly  the  most  numerous  and  ubiquitous  and 
the  most  "  domestic"  in  its  habits,  and  it  is  rightly  suspected 
of  playing  a  larger  part  as  the  mere  passive  carrier  of  disease 
germs  than  is  any  other  insect. 

Flies  seen  to  carry  Infective  Material.  —  A  large  number 
of  observers,  noting  the  passage  of  flies  from  infected  matter 
to  human  beings  or  to  food,  have  become  convinced  that 
these  insects  are  important  carriers  of  disease.  According  to 
Nuttall,  Budd  as  long  ago  as  1862  considered  it  proved  that 
Egyptian  ophthalmia  is  carried  from  child  to  child  by  the 
flies  that  can  be  observed  in  great  numbers  crawling  over  the 
face  and  eyes.  Laveran  noted  the  same  conditions  in  Biskra, 
and  he  and  many  others  believe  that  oriental  sore  is  spread 
in  the  same  way.  Nuttall  also  cites  several  of  the  earlier 
writers  as  believing  that  anthrax,  cholera  and  plague  are 
transmitted  by  flies.  After  the  development  of  bacteriology 
and  the  observations  and  experiments  referred  to  above  as 
to  the  power  of  flies  and  similar  insects  to  transport  bacteria, 
considerable  weight  was  added  to  the  arguments  of  those  who 
saw  in  this  mode  of  transmission  an  important  factor  in  the 
distribution  of  the  infectious  diseases. 

Tuberculosis. 

Due  to  Flies.  —  Cobb  ^  watched  flies  passing  from  tuber- 
culous sputum  to  food,  and  he  attributes  to  these  insects  a 
large  proportion  of  tuberculosis  in  man.  Many  health  officials 
and  anti-tuberculosis  leagues  have  issued  lurid  bulletins  illus- 
trating the  agency  of  flies  in  transmitting  the  germs  of  "  the 
great  white  plague."  While  it  is  certainly  possible  for  the 
disease  to  be  transmitted  in  this  way,  there  is  absolutely  no 

1  Cobb,  Am.  Med.,  Phila.,  1905,  IX,  475. 


INFECTION  BY  INSECTS  357 

evidence  that  it  is  a  factor  of  appreciable  importance.  The 
opportunities  for  infection  with  tubercle  bacilli  in  other  ways 
are  so  much  greater  and  more  numerous  that  we  are  not 
justified  in  considering  infection  by  flies  of  much  importance. 

Cholera. 

Due  to  Flies.  —  Cholera  has  of  late  been  considered  to  be 
to  a  considerable  extent  a  fly-borne  disease.  This  has  been 
the  view  of  Chantemesse  and  Borel/  as  well  as  of  many  of  our 
officials  in  the  Philippines,^  as  Heiser,^  Woodruff  *  and  Mc- 
Laughlin,^ though  all  of  the  latter  seem  to  consider  contact 
infection  a  good  deal  more  important  than  infection  by  means 
of  flies.  Nuttall  cites  Flijgge,  Macrae,  Buchanan,  and  Tsu- 
zuki  as  considering  flies  of  great  importance  in  this  disease. 

Dysentery. 

Due  to  Flies.  —  In  a  recent  outbreak  of  dysentery  in  a 
Massachusetts  asylum  involving  156  cases,  and  carefully 
studied  by  Ryder,"  flies  were  believed  to  be  the  chief  factor 
in  the  extension  of  the  disease. 

Diarrhea. 

Due  to  Flies.  —  Many  of  the  English  have  been  inclined 
to  attribute  considerable  influence  to  the  fly  as  a  factor  in  the 
causation  of  the  summer  diarrheas  of  infants.  Newsholme, 
who  believes  that  diarrhea  is  due  chiefly  to  infection  of  the 
milk  in  the  house,  says  that  opened  cans  of  condensed  milk 
are  often  seen  to  be  black  with  flies,  attracted  by  the  sugar 
in  the  milk,  and  attributes  to  them  no  inconsiderable  share  in 
the  causation  of  the  disease.     Sandilands,^  like  Newsholme, 

'  Chantemesse  and  Borel,  Bull.  Acad.  de.  m€d.,  Par.,  1905,  3  s.,  LIV, 
252. 

»  Maus,  Abst.,  Med.  News,  N.  Y.,  1902,  LXXXI,  318. 
»  Heiser,  J.  Am.  M.  Ass.,  Chicago,  1907,  XLVIII,  856. 
«  Woodruff,  J.  Am.  M.  Ass.,  Chicago,  1905,  XLV,  1160. 
»  McLaughlin,  J.  Am.  M.  Ass.,  Chicago,  1909,  LII,  1153. 
«  Ryder,  Boston  M.  &  S.  J.,  1909,  CLXI,  681. 
^  Sandilands,  J.  Hyg.,  Cambridge,  1906,  VI,  77. 


358       THE  SOURCES  AND  MODES  OF  INFECTION 

finds  diarrhea  especially  prevalent  among  the  users  of  con- 
densed milk,  and  he  thinks  that  the  milk  is  probably  infected 
by  flies  after  the  can  is  opened.  Nuttall  cites  Copeman  as 
seeing  in  flies  the  possible  cause  of  an  outbreak  of  diarrhea 
investigated  by  him.  Nash  ^  in  1903  stated  his  belief  that 
the  house  fly  played  the  chief  part  in  the  epidemiology  of 
summer  diarrhea. 

Typhoid  Fever. 

Flies  in  Spanish  War.  —  More  attention  has,  however,  been 
bestowed  on  the  relation  of  the  fly  to  typhoid  fever  than  to 
any  other  disease.  Sedgwick  ^  was  the  first  that  I  know  of 
to  call  attention  to  the  importance  of  flies  as  a  means  of 
spreading  typhoid  fever,  but  the  excessive  typhoid  death  rate 
in  the  home  camps  of  our  soldiers  during  the  Spanish-Ameri- 
can War  did  more  than  anything  else  to  call  attention  to  the 
possible  importance  of  the  fly  as  a  distributer  of  the  germs  of 
this  disease.  Surgeon  General  Sternberg  had  issued  orders  to 
guard  against  flies,  but  they  had  little  effect.  Veeder^  clearly 
set  forth  the  possibility  of  the  transfer  of  fecal  matter  to 
food  by  means  of  flies,  and  he  declared  that  flies  were  the 
principal  cause  of  the  prevalence  of  the  disease  in  the  camps. 
The  report  of  the  commission  to  investigate  the  cause  of  the 
fever,  although  laying  chief  stress  on  contact  infection,  for- 
cibly emphasized  the  part  played  by  flies  in  the  spread 
of  the  disease.^  Vaughan,  a  member  of  the  commission,  per- 
sonally urged  the  importance  of  flies  in  the  spread  of  this 
disease.^  Ever  since,  great  popular  and  scientific  attention 
has  been  bestowed  upon  the  fly  in  the  United  States  and  also 
in  other  countries. 

1  Nash,  J.  San.  Inst.,  Lond.,  1903,  XXVI,  495. 

2  Sedgwick,  Rep.  Bd.  Health  [etc.],  Mass.,  1892,  736. 

3  Veeder,  Med.  Rec,  N.  Y.,  1898,  LIV,  429. 

*  Abst.  of  Rep.  on  the  Origin  and  Spread  of  Typhoid  Fever  in  U.  S. 
Military  Camps  during  the  Spanish  War,  1898,  183. 

6^ Vaughan,  J.  Am.  M.  Ass.,  Chicago,  1900,  XXXIV,  1451,  1496. 


INFECTION  BY  INSECTS  359 

Other  Reports  of  Typhoid  Fever  Due  to  Flies.  —  Nuttall 
cites  Quill,  Tooth  and  Calverly,  Smith,  Austen,  Straton  and 
Jones  as  attributing  much  of  the  army  typhoid  in  South 
Africa  and  India  to  the  presence  of  flies.  Numerous  writers 
on  typhoid  fever  in  civil  life  have  referred  to  the  fly  as  a 
most  active  agent  in  the  transmission  of  this  disease.  In 
"  The  House  Fly  at  the  Bar,"  published  by  the  Merchants' 
Association  of  New  York  in  1909,  are  printed  opinions  of 
seventy  or  more  health  officials  and  others,  all  but  nine  or 
ten  of  whom  are  emphatic  in  their  statements  that  flies  are 
very  important  carriers  of  disease  germs.  Some  few,  how- 
ever, consider  that  the  case  against  the  fly  has  not  been 
proved,  though  some  circumstances  are  suspicious.  Several 
give  instances  of  fly  infection  that  have  come  to  their  notice. 
Hurty  writes  of  an  outbreak  in  an  asylum  following  the  brief 
use  of  the  privy  by  a  walking  case  of  typhoid  fever.  Flies 
abounded  and  there  was  no  chance  for  contact.  Taylor,  of 
Denver,  reported  typhoid  fever  at  a  dairy.  The  milk  became 
infected,  he  thinks  by  flies,  for  the  privy  was  near  the  milk 
house,  and  gelatine  cultures  exposed  near  the  privy  and  in  the 
milk  house  showed  colonies  of  typhoid  bacilli,  presumably 
deposited  by  flies!  Dr.  H.  W.  Hill,  the  exceedingly  cautious 
epidemiologist  of  the  Minnesota  State  Board  of  Health,  writes 
me  that  from  his  observations  in  that  state  he  "  firmly 
believes  that  flies  are  an  important  factor  in  the  spread  of 
typhoid  in  such  places  as  mining  and  lumber  camps,  and  that 
the  small  country  village  with  its  exposed  outdoor  closets 
parallels  the  camp  conditions  exactly."  He  further  states 
that  Wald  noted  that  in  a  certain  camp  the  Italians  did  not 
contract  the  disease  because,  as  he  thought,  they  did  not  eat 
between  meals,  while  the  Finns  suffered  severely  because 
they  kept  their  food  laid  out  on  the  table  all  the  time,  where 
it  was  exposed  to  innumerable  flies,  and  helped  themselves 
during  the  day  at  random.  Numerous  bulletins  and  circulars 
have  been  issued  by  state  and  municipal  health  officials,  some 
of  which  depict,  in  exaggerated  language  and  with  extrava-j 


360       THE  SOURCES  AND  MODES  OF  INFECTION 

gant  illustration,  the  danger  to  be  feared  from  this  household 
pest,  and  a  distinguished  entomologist  has  urged  that  the 
familiar  name  of  M.  domestica  be  changed  from  house  fly 
to  typhoid  fly. 

The  Fly  a  Nuisance.  —  While  the  fly  is  a  nuisance  and 
it  is  highly  desirable  to  get  rid  of  it,  and  while  it  seems  likely 
that  it  is  to  some  extent  a  means  of  spreading  disease,  it  is 
extremely  unwise  to  make  definite  statements  that  it  is  the 
chief  source  of  diarrhea,  of  cholera  or  of  typhoid  fever,  unless 
we  have  very  exact  proof,  and  it  is  unwise,  unless  such  proof 
is  at  hand,  to  urge  large  expenditures  to  get  rid  of  flies, 
promising  thereby  the  eradication  of  typhoid  fever  and  other 
diseases.  If  it  should  chance  that  a  mistake  has  been  made, 
and  that  the  fly  is  not  the  chief  disseminator  of  typhoid  fever, 
and  the  disease  still  persists  after  the  fly  has  disappeared, 
we  need  not  be  surprised  if  the  public  fail  to  take  us  seriously 
when  we  advise,  on  knowledge  that  is  well  established,  that 
mosquitoes  are  the  sole  carriers  of  malaria  and  yellow  fever; 
that  escape  from  the  tsetse  fly  means  escape  from  sleeping 
sickness;  and  that  a  rat-proof  city  will  be  a  plague-proof  city. 

Flies  suspected  from  their  Habits.  —  The  chief  reasons 
why  the  fly  is  believed  to  be  the  carrier  of  diarrhea,  cholera 
and  typhoid  fever  are  that  flies  are  seen  to  pass  from  feces 
to  food;  that  they  have  been  shown  to  carry  fecal  bacteria, 
and  in  several  instances  the  specific  bacteria  of  cholera  and 
typhoid  fever ;  and  that  they  often  swarm  in  unusual  numbers 
at  times  and  in  places  where  there  is  an  exceptional  preva- 
lence-of  disease.  The  very  definite  observations  of  Hamilton, 
Fricker,  Klein,  Simmonds,  Mann  and  Tsuzuki  as  to  the  find- 
ing of  infected  flies  in  infected  houses,  and  the  accounts  given 
by  Veeder,  Vaughan,  Tooth,  Smith,  Hill  and  others,  of  the 
contamination  of  food  by  flies  in  camps,  military  and  civil, 
certainly  render  it  probable  that  these  insects  do  at  times 
cause  sickness,  and  may  under  certain  conditions  such  as 
prevail  in  camps  be  an  important  factor  in  outbreaks.  But 
these  observations  are  far  from  a  demonstration  of  what  is 


INFECTION  BY  INSECTS  361 

now  generally  claimed,  that  flies  are  the  chief  factor  in  the 
spread  of  typhoid  fever,  and  perhaps  of  summer  diarrhea,  in 
well-ordered  civil  communities. 

Diarrhea.  Statistical  Evidence  of  Fly  Infection.  —  At- 
tempts have  been  made  to  prove  by  the  statistical  method 
the  relation  of  flies  to  disease.  Observations  made  in 
widely  different  localities  have  shown  a  very  close  relation 
between  the  seasonal  distribution  of  flies  and  summer  diarrhea. 
Stations  are  established  at  various  places  in  a  town  and  flies 
are  caught  in  traps  or  by  means  of  fly  paper,  and  the  number 
of  flies  is  compared  with  the  number  of  deaths  from  diarrhea. 
Niven^  in  Manchester,  in  1903,  found  that  the  '*  fly  curve" 
and  the  curve  for  diarrheal  deaths  corresponded  very  closely, 
and  the  same  agreement  was  noted  in  1905  and  1906.^  The 
table  given  shows  both  the  date  of  inception  and  the  date  of 
death  of  the  fatal  cases  of  diarrhea.  In  both  years  the  max- 
imum number  of  cases  occurred  at  almost  exactly  the  same 
time  as  the  maximum  number  of  flies,  and  the  maximum  num- 
ber of  deaths  about  a  week  later.  In  1905  the  maximum  was 
about  August  1,  and  in  1906  about  September  5.  Jackson  in 
New  York  ^  showed  a  similar  close  relation  between  flies  and 
diarrhea,  as  has  Ainsworth  *  for  Poona  in  India.  Nash,^ 
showing  the  seasonal  distribution  of  flies,  states  that  in  1902, 
at  Southend,  there  were  few  flies  and  little  diarrhea  in 
August,  and  that  diarrhea  increased  in  September  as  the  flies 
increased.  Both  1902  and  1903  had  cool  summers  with  few 
flies  and  little  diarrhea,  while  1904  and  1906  had  plenty  of 
flies  and  plenty  of  diarrhea.  In  1904  there  was  a  heavy  local 
incidence  near  a  large  dump  where  flies  abounded.     Hamer  ^ 

»  Niven,  Rep.  on  Health  of  Manchester,  1903,  123. 
2  Rep.  on  Health  of  Manchester,  1906,  82. 

'  Jackson,  Rep.  to  Com.  on  Pollution  [etc.],  of  the  Merchants'  Ass. 
of  N.  Y.,  1907,  17. 

*  Ainsworth,  J.  Roy.  Army  Med.  Corps,  Lond.,  1909,  XII,  485. 
«  Nash,  J.  Hyg.,  CambridRe,  1909,  IX,  141. 

•  Hamer,  Rep.  Med.  Oflf.  Health,  Co.  of  Lond.,  1907,  Append.  II. 


362       THE  SOURCES  AND  MODES  OF  INFECTION 

made  a  careful  study  of  the  seasonal  distribution  of  flies  in 
London,  and  he  shows  that  while  there  is  an  apparent  agree- 
ment between  the  fly  curve  and  that  of  diarrheal  deaths,  the 
latter  begins  to  fall  before  the  former,  which  it  could  scarcely 
do  if  flies  were  the  chief  cause  of  the  disease.  Hamer  is  of 
the  opinion  that  both  phenomena  are  dependent  on  tempera- 
ture. In  Providence,  in  1909,  Sykes  ^  has  shown  that  the 
maximum  number  of  deaths  from  diarrheal  diseases  occurred 
about  two  weeks  earlier  than  the  maximum  fly  catch.  Jack- 
son in  his  report  has  a  map  on  which  are  located  all  the  deaths 
from  intestinal  disease.  This  map  shows  that  the  great  bulk 
of  these  are  at  no  great  distance  from  the  water  front,  where 
the  flies  swarmed  about  the  sewer  outlets.  It  is  just  there 
that  the  tenements  crowded  with  poor  children  are  situated, 
and  to  maintain  his  argument  it  would  be  necessary  to  show 
an  excess  over  and  above  the  excess  of  diarrhea  always  found 
in  tenements,  and  to  eliminate  the  other  unfavorable  factors 
associated  with  poverty. 

Evidence  not  Conclusive.  —  Although  there  is  consider- 
able evidence  of  a  close  parallelism  between  the  seasonal  dis- 
tribution of  flies  and  of  diarrhea,  this  parallelism  is  no  proof 
that  the  latter  is  dependent  upon  the  former.  Even  as  cor- 
roborative evidence  it  has  little  value.  The  return  of  the 
sun  from  the  equator  results  in  a  great  variety  of  phenomena, 
many  of  which,  though  closely  related  in  time,  have  no  causa- 
tive relation  one  with  another.  The  presence  of  flies  seems 
to  be  closely  correlated  with  the  temperature,  though  it  may 
be  that  the  connection  is  far  from  direct.  So  also  are  a  vast 
number  of  other  events  correlated  with  the  temperature, 
though  they  have  no  causative  connection  with  flies.  A  few 
years  ago  it  was  discovered  that  summer  diarrhea  developed 
only  when  the  temperature  of  the  soil  had  reached  a  certain 
point,  and  this  was  by  many  considered  a  demonstration 
that  the  germs  of  the  disease  developed  in  the  soil.  Now  it 
is  the  fashion  to  say  that  diarrhea  is  due  to  flies  because  at 
^  Sykes,  Rep.  Supt.  Health,  Providence,  1909,  15. 


INFECTION  BY  INSECTS  363 

times  the  increase  in  flies  precedes  by  a  little  the  increase  in 
diarrhea.  While  it  may  be  that  flies  have  much  to  do  with 
the  causation  of  infantile  summer  diarrhea,  as  yet  we  have 
no  proof  of  it. 

Flies  and  Typhoid  Fever.  Statistical  Evidence.  —  As  the 
seasonal  distribution  of  flies  has  been  studied  with  reference 
to  diarrhea,  so  has  it  been  studied  with  reference  to  typhoid 
fever.  Jackson,  in  his  report  to  the  Merchants'  Association 
in  New  York  before  referred  to,  gives  a  chart  showing  the 
seasonal  distribution  of  flies  in  New  York  and  of  deaths 
from  typhoid  fever,  the  latter  being  set  back  two  months  to 
allow  for  the  assumed  time  between  the  date  of  infection  and 
the  date  of  death.  The  apex  of  the  tj^phoid  curve  corre- 
sponds fairly  well  with  the  apex  of  the  fly  curve,  but  there  is 
a  rise  in  the  typhoid  curve  in  February,  two-thirds  as  high  as 
that  of  August,  which  certainly  cannot  be  attributed  to  flies. 
Ainsworth  in  India*  states  that  at  Poona  the  maximum 
admissions  of  typhoid  fever  to  the  hospital  occur  about  one 
month  after  the  maximum  fly  catch.  Judging  from  Ains- 
worth's  paper,  there  appears  to  be  great  seasonal  variation 
in  the  number  of  flies  in  Poona,  correlated  closely  with  the 
temperature,  as  with  us. 

Statistical  Evidence  against  Theory.  —  Niven^  found  that 
while  in  Manchester  in  1903  the  maximum  number  of  flies 
was  caught  about  August  29,  the  maximum  number  of 
cases  of  typhoid  was  not  reached  until  November,  during  the 
whole  of  which  month  the  morbidity  remained  high.  In 
1906  ^  there  was  as  usual  a  well-marked  maximum  of  flies 
about  September  1,  and  while  the  typhoid  morbidity  was 
high  in  September,  being  65,  it  was  .somewhat  higher  in  Oc- 
tober, and  there  were  46  ca.ses  in  November  and  50  in  January 
and  only  21  in  July  and  23  in  August.     In  Washington,* 

»  Ainsworth,  .J.  Roy.  Army  Med.  Corps,  Lond.,  1909,  XII,  485. 

2  Xiven,  Hop.  on  Health  of  Manchester,  190.3,  123. 

'  Rep.  on  Health  of  Manchester,  1906,  63,  84. 

*  U.  S.  Pub.  Health  &  Mar.  Hos.  Serv.,  Hyg.  Lab.  Bull.,  No.  52,  30. 


364       THE  SOURCES  AND  MODES  OF  INFECTION 

in  1908,  the  maximum  fly  catch  was  for  the  week  ending 
June  24,  after  which  it  steadily  and  rapidly  decreased. 
The  maximum  of  typhoid  cases,  according  to  date  of  at- 
tack, was  in  the  week  ending  July  22,  but  instead  of  falling 
rapidly,  as  did  the  fly  catch,  it  continued  high  until  the 
middle  of  September.  There  certainly  is  little  parallelism 
between  the  two  curves.  The  commissioners  appointed  to 
study  the  disease,  and  who  make  the  report,  say  that  the 
evidence  is  quite  strong  that  flies  play  a  relatively  small  part 
in  the  spread  of  typhoid  fever  in  Washington. 

In  Providence  the  seasonal  distribution  of  typhoid  fever 
cases,  according  to  date  of  first  symptoms,  for  the  six  years 
1904-1909,  was  as  follows.  All  cases  due  to  milk  and  all 
certainly  contracted  out  of  the  city  are  excluded. 


Jan. 

Feb. 

Mar. 

Apr. 

May 

June 

45 

36 

26 

48 

49 

56 

July 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

80 

161 

133 

117 

96 

59 

According  to  observations  of  Sykes,  the  maximum  fly  catch 
out  of  doors  was  about  the  last  of  July,  when  it  began  to  fall 
off  quite  rapidly.  The  observations  as  to  the  indoor  catch 
were  not  very  numerous,  but  it  seems  probable  that  the  flies 
go  indoors  in  greater  numbers  as  the  weather  grows  cooler  in 
September.  There  is  certainly  not  a  very  close  agreement 
between  the  number  of  flies  and  the  prevalence  of  typhoid 
fever.  It  is  scarcely  possible  that  the  typhoid  fever  develop- 
ing in  November  is  due  to  flies,  and  yet  there  were  96  cases 
in  November,  and  the  November  rate  is  higher  than  that 
of  any  other  month  except  August,  September  and  October. 
If  we  cannot  attribute  the  excess  in  November  to  flies,  why 
should  it  be  thought  necessary  to  attribute  the  excess  of 
the  preceding  three  months  to  flies?  I  can  see  nothing  in 
the  seasonal  distribution  of  typhoid  fever  in  Providence  to 


INFECTION  BY  INSECTS  365 

warrant  the  assumption  that  flies  are  an  important  factor  in 
its  causation. 

Local  Variation  in  Fly  Distribution.  —  One  of  the  most 
interesting  of  Sykes'  observations  was  the  enormous  variation 
in  the  local  distribution  of  flies.  In  some  of  the  dirtiest 
sections  of  the  city  the  fly  catch  was  25  or  30  times  as  great 
as  in  the  clean  parts,  and  the  difference  in  the  indoor  catch 
was  still  greater.  While  there  is  somewhat  more  typhoid 
fever  in  the  fly-infested  districts,  the  difference  is  not  very 
marked,  and  a  considerable  excess  there  might  be  expected 
as  a  result  of  contact  infection  due  to  the  uncleanly  habits 
of  the  poorer  people.  There  is  therefore  nothing  in  the 
local  distribution  of  flies  in  Providence  to  warrant  a  belief 
that  they  have  much  to  do  with  the  spread  of  typhoid 
fever. 

Correlation  of  Typhoid  Fever  and  High  Temperature.  — 
I  have  been  able  to  find  only  the  very  few  observations  noted 
above  as  to  the  correlation  of  fly  distribution  and  typhoid 
fever,  and  these  few  do  not  indicate  that  there  is  any  reason 
to  assume  that  the  flies  stand  in  causative  relation  to  the 
fever.  The  very  careful  work  of  Sedgwick  and  Winslow  ^ 
shows  that  throughout  the  world,  and  in  both  hemispheres, 
there  is  a  distinct  relation  between  this  disease  and  the  sea- 
sonal rise  in  temperature.  These  authors,  though  they  recog- 
nized a  certain  amount  of  infection  by  flies,  explained  the 
autumnal  increase  in  typhoid  fever  as  due  to  the  direct  and 
favorable  action  of  high  temperature  on  the  life  of  the  bacillus 
outside  the  body.  This  view  hardly  seems  tenable  from  what 
has  since  been  learned  of  the  life  habits  of  the  bacillus,  and  I 
think  is  now  no  longer  held  by  the  authors.  It  is  the  custom 
now  for  most  writers  to  attribute  to  flies  the  chief  role  in  the 
autumnal  excess  of  typhoid  fever,  but  from  the  evidence  at 
hand  it  seems  wiser,  while  admitting  the  fact  of  seasonal  dis- 
tribution, as  determined  by  Sedgwick  and  Winslow,  to  await 

>  Sedgwick    and   Winslow,    Mem.  Am.  Acad.  Arts.  &  Sc,   1902, 
XII,  No.  5. 


366       THE  SOURCES  AND  MODES  OF  INFECTION 

further  study  before  attributing  this  definitely  to  any  one 
cause  or  group  of  causes. 

Control  of  Flies.  —  Nevertheless  flies  are  a  great  nuisance 
and  a  possible  source  of  danger,  and  it  is  very  desirable  that 
they  should  be  eliminated  as  far  as  possible.  Each  indi- 
vidual family  can  very  effectually  control  these  pests  by 
good  screening  and  the  use  of  fly  paper.  It  is  desirable  that 
people  should  be  educated  to  dislike  flies.  Chantemesse  says 
that  the  housewife  should  think  it  as  much  of  a  discredit  to 
have  flies  in  her  house  as  bugs  in  her  bed.  Circulars  of 
information  may  be  distributed,  but  care  should  be  taken  to 
avoid  exaggeration,  and  not  to  promise  too  much  either  as 
to  the  effectiveness  of  remedies  or  the  resulting  decrease  in 
disease.  We  know  even  now  far  too  little  about  the  habits 
of  flies  and  the  best  ways  of  attacking  them.  Packard  and 
Howard  gave  us  our  first  definite  knowledge,  but  this  has 
been  much  extended  by  Newstead,^  who  showed  that  the  fly 
is  far  less  exclusive  in  its  choice  of  breeding  places  than  was 
supposed.  Austen,  Jackson,  Sykes,  Jepson  and  Hamer  have 
also  added  to  our  knowledge.  It  appears  that  effective  scav- 
enging is  the  most  important  means  of  getting  rid  of  flies. 
If  yards,  streets  and  vacant  lots  were  kept  clean,  market  refuse 
removed  promptly,  and  all  garbage  kept  covered,  there  would 
be  an  enormous  reduction  in  the  number  of  flies  about  dwell- 
ings. The  most  practicable  way  to  prevent  the  breeding  of 
flies  in  stable  manure  is  to  compel  its  removal  once  a  week. 
Wherever  it  is  possible  the  privy  vault  should  be  abolished. 
When  this  is  impossible,  the  fly-proof  privy  has  been  urged. 
To  the  writer  this  scarcely  seems  feasible,  but  Levy  in  Rich- 
mond is  making  a  strong  fight  for  it,  and  his  efforts  will  be 
watched  with  interest.  The  question  of  covering  food  in 
markets  and  shops  to  protect  it  from  flies  as  well  as  from 
dust  has  been  much  discussed.     Slack ^  in  an  excellent  paper 

1  Newstead,  Rep.  on  the  Habits,  etc.,  of  the  House  Fly,  to  the  Health 
Committee,  Liverpool,  1907. 

2  Slack,  Am.  J.  Pub.  Hyg.,  1909,  V,  159. 


INFECTION  BY  INSECTS  367 

concludes  that  the  danger  from  this  source  in  a  well-ordered 
city  is  not  very  great,  but  that  for  aesthetic  reasons  the  public 
might  well  demand,  through  ordinances  or  otherwise,  that 
food  be  so  protected.  In  this  opinion  the  writer  heartily 
concurs. 

Summary.  —  After  this  brief  examination  of  the  evidence 
in  regard  to  the  role  of  insects  in  the  transmission  of  disease 
we  are  justified  in  the  following  conclusions: 

First.  It  is  certain  that  yellow  fever  and  malaria  are  trans- 
mitted solely  by  certain  mosquitoes,  and  that  by  controlling 
the  mosquitoes  it  is  possible  even  under  very  unfavorable 
conditions,  to  eradicate  or  reduce  to  a  minimum  these  two 
diseases. 

Second.  It  is  highly  probable  that  the  relapsing  fevers  are 
transmitted  solely  by  certain  ticks,  sleeping  sickness  by  the 
tsetse  fly,  and  filariasis  by  the  mosquito. 

Third.  Bubonic  plague  in  human  beings  is  usually  trans- 
mitted from  rat  to  man  by  the  flea. 

Fourth.  It  is  probable  that  under  certain  conditions,  as 
in  military  and  civil  camps,  and  in  filthy  communities  without 
sewerage,  insects,  especially  flies,  may  be  an  important  factor 
in  the  spread  of  the  fecal-borne  diseases,  but  there  is  no  evi- 
dence that  in  the  average  city  the  house  fly  is  a  factor  of 
great  moment  in  the  dissemination  of  disease. 


INDEX 

Page 

Actinomycosis 306 

African  cattle  fever 84 

Air,  see  Sewer  air. 

bacillus  influenzEe  not  carried  by 71-72 

bacillus  tuberculosis  in 248-249 

bacteria  found  in 248-251 

danger  of  infection  by 250 

expired,  free  from  germs 237 

infection  by,  thought  important 95 

infection  of  wounds  by 250-251 

pneumococcus  in 250 

pus-forming  bacteria  in 249-250 

swine  plague  bacilli  in 250 

Air  infection,  conclusions 263-265 

experiments  with  anthrax 262 

Mediterranean  fever 261-262 

plague 262-263 

Air-borne  anthrax 235-236 

influenza  is  not 231-232 

malaria  is  not 324 

measles 232 

chicken  pox 224 

disease,  slight  evidence  of 236 

infection  indoors 232 

infection  in  surgery 233-234 

infection,  reasons  for  belief  in 213-214,  233 

scarlet  fever 224-227 

out  of  doors 226-227 

smallpox,  cases  traced  to  other  sources 222-223 

conclusions 223-224 

evidence  against 220-223 

evidence  of,  in  United  States 218-219 

from  hospitals 214-224 

infection  of,  denied 217-224 

objections  to  theory 219-220 

tuberculosis..  . 152,  160-161 

Amebse,  intestinal  parasites 83 

species  of 20 

Amebae  dysenterite  carriers,  percentage  of 88-89 

grown  on  culture  media 20 

in  soil 20 

in  well  persons 87-88 

on  vegetables 20 

Amebic  dysentery 20 

369 


370  INDEX 

American  hospitals 100-103 

Anchylostoma,  see  Uncinaria,  Hookworms. 

Anchylostoma  duodenalis I44 

Anchylostomiasis,  due  chiefly  to  contact 144-145 

Animals,  diseases  of,  affecting  man 311-313 

Animals  spread  tuberculosis  by  licking  one  another 162 

Anopheles  mosquitoes  carry  malaria 322-323 

mosquitoes,  species  and  habits 325-326 

Anthracosis 256-257 

Anthrax,  a  dust-born  disease 235-236 

an  air-borne  disease 235-236 

experiments  in  infection  by  air 262 

perpetuated  by  direct  contact 2 

soil  in  relation  to 2 

spread  by  unrecognized  or  concealed  cases 2 

Anthrax  and  fomites 184-185 

insects 349-350,  356 

due  to  food  infection 2,  305 

bacillus,  see  Bacillus  anthracis. 

from  hair,  hides 185 

morocco  factories 3 

wool 185 

wool  refuse > 3 

spores  in  dust,  hair,  hides,  wool 184-185 

Antisepsie  medicale  in  French  hospitals 156 

Antitoxin  may  favor  spread  of  disease 326-327 

Ants  carry  Bacillus  murium  typhi 355 

plague  bacilh 351 

Aspergillus  destroys  mosquitoes 330 

Asylums,  bacillary  dysentery  in 141-142 

percentage  of  bacillus  diphtheria?  carriers  in 62 

typhoid  fever  in 37 

Atoxyl  to  prevent  sleeping  sickness 342 

Babies'  Hospital,  gonorrhea  in 123-124 

Bacillary  dysentery  caused  by  contact 43,  141-142 

culture  of  bacillus  in  eye 141-142 

in  camps 141 

in  institutions 141-142 

dysentery,  mild  cases  of 43 

Bacillus  anthracis,  see  Anthrax  spores. 

Bacillus  anthracis,  growth  in  ponds 3 

relation  to  the  soil . . 2,  4 

saprophytic  existence  of 2 

Bacillus  coli  communis  cause  of  diarrhea 307 

in  dust  of  schoolrooms 244 

on  the  hancls 137 

Bacillus  diphtherise,  carriers  in  family 61-62 

in  insane  asylum 62 

in  schools 62-66 

of 54-71 

carriers,  investigation  of,  in  Massachusetts  .       55 
in  carriers,  varieties  of 55 


INDEX  371 

Page 

Bacillus  diphtherige  in  carriers,  virulence  of 54,  56-58,63-64 

found  intermittently 70 

in  bread 22 

clay 191 

convalescents 54,  56-57,  70-71 

dust 240,244 

holy  water,  on  cups,  pencils,  drinking  glass     150 

membrane 198 

milk 21,22 

otitis 66-67 

pupils  cause  disease  in  teacher 70 

rhinitis 66-67 

rooms 191,  199 

scarlet  fever 58-60,  63,  68 

school  children 54-58,  60,  62-66 

soil 22 

sore  throats 65-66,  70-71 

well  persons 54-55 

may  be  air-borne 239 

not  in  normal  throats 56-57 

on  coat 185 

drinking  glass 150 

fomites 150-151,  185,  198-199 

fomites,  virulence  of 198 

pencils 151,  191 

resistance  to  drying 191,  240 

saprophytic  existence  of 21 

Bacillus  dysenteria?,  cause  of  diarrhea 307 

in  convalescents 43 

feces 20 

milk 11 

soil 19 

well  persons 43 

resistance  to  drying 192 

saprophj'tic  existence  of 19 

Bacillus  enteritidis,  cause  of  diarrhea 307 

in  food  poisoning 311 

Bacillus  enteritidis  sporogenes,  cause  of  diarrhea 307 

Bacillus  influenzaj  in  droplets 248 

not  carried  by  air 71-72 

widely  distributed 72-73 

Bacillus  influenzae,  not  saprophytic 22 

persistence  of 72 

resistance  to  drying 196 

Bacillus  leprae  in  droplets 247 

Bacillus  morbificans,  in  food  poisoning 311 

Bacillus  paratyphi,  cause  of  diarrhea 307 

Bacillus  paratyphi  in  feces 12 

in  food  poisoning 311 

not  found  in  healthy  persons 39 

Bacillus  pestis  carried  by  ants 351 

in  bodies  of  fleas 194 

convalescent  guinea  pigs 42 


372  INDEX 

Page 

Bacillus  pestis  in  convalescents 42 

cow  dung 19 

dust 240-241 

sputum 42 

not  found  on  floors 193 

on  cotton  goods 186 

Bacillus  pestis,  infection  of  soil  by 18 

resistance  to  drying 193-194,  240-241 

saprophytic  existence  of 18 

Bacillus  prodigiosus  on  flies 354 

in  droplets 245-247 

in  sewer  air 234 

Bacillus  tetani  in  blank  cartridges 6, 184 

dirt  of  floors 197 

gelatine 6,  184 

intestines  of  animals 5 

soil 6,197 

on  lamp  wick 6, 184 

Bacillus  tetani,  latency  of 78 

resistance  of 6,  183-184 

saprophytic  existence  of 6 

Bacillus  tuberculosis,  carriers  of 75-77 

latency  of 76-77 

not  saprophytic 22 

so  resistant  as  believed 192-193 

proportion  of  human  and  bovine  types  . .  300-301 

resistance  to  drying 192-193,  199-200,  241 

Bacillus  tuberculosis  in  air 248-249 

butter 304-305 

communion  cups 153 

droplets 245-246 

dust 242-243 

flies,  and  fly  specks , 353-354 

lymphatic  glands 161 

milk 295-296 

nose  and  mouth 75-76  151, 161 

railway  carriages 242 

room 193,  242 

tonsils 161-162 

tramcaf  s 242 

may  be  dust-borne 239-240 

pass  from  stomach  to  lungs 255-258 

not  found  in  street  dust 242 

in  expired  air 237 

on  spirometer 153 

on  a  glass 153 

dishes 153 

fomitea 152-153,  199-200,  242,  243 

hands 151-152 

napkin  rings 153 

sidewalks 152 

telephones 153 

toiigue 161 


INDEX  373 

Page 

Bacillus  tuberculosis  perishes  in  light 192-193 

swept  from  sidewalks  by  dresses 152 

Bacillus  typhi,  carriers  of,  never  sick 31-37 

flies  and 352-353 

intermittent  excretion  of 36 

moisture  necessary  to  growth  of 12 

path  of  entrance 30,  136 

resistance  to  drying 190-191,  240 

saprophytic  existence  of 7,  12 

Bacillus  typhi  carried  on  fingers 127-128 

in  bone  marrow 31 

bones 30 

bronchial  mucus 30 

butter 12 

cerebro-spinal  fluid 30 

dead  animals 8 

dust ■ 240 

feces 8,  31-32 

gall  bladder 30 

ice 10,  269 

kidneys 30 

milk 11 

ovaries 30 

oysters 10 

privy  vaults 8 

seltzer  water 10 

septic  tank  effluent 8 

sewage 8 

sew  er  air 234 

soft  drinks 10 

soil 7 

epidemiological  evidence  of  growth 12 

spleen 31 

the  blood 30 

tidal  mud 8 

urinary  bladder 30 

urine 31 

water 9 

water,  epidemiological  evidence  of  growth 13 

modes  of  contamination 270 

recovered  from 269 

increase  in  milk 13 

on  blankets 185 

Bacteria  and  sewer  air 234-235,  238-239 

Bacteria,  effect  of  drying  upon 189-190 

inhalation  of 254-255 

Bacteria  found  in  air 248-251 

in  mouth 150 

not  found  in  expired  air 237 

not  given  off  from  moist  surfaces 237-238 

of  suppuration,  see  Pus  bacteria. 

on  cups 150-151 

fomites 197-200 


374  INDEX 

Page 

Bacteria  on  pencils  150-151 

money 181-182 

hands 150-152 

Bagging,  yellow  fever  from 171 

Balantidium 83 

Ballast,  yellow  fever  from 171 

Bathing,  typhoid  fever  from 274-275 

Baths,  public,  encourage  cleanliness 169 

Bedbugs  and  anthrax 350 

plague 347 

relapsing  fever 344-345 

typhoid  fever 351 

kala-azar 342 

Bed  clothing,  bacillus  diphtheria;  on 198 

Bedpan  carries  dysentery  ameba; 141 

Bed,  smallpox  from 172 

Betel  nut,  cholera  spread  by 143 

Biological  carriers  distinguished  from  mechanical  carriers 346 

Black-leg 4 

Blank  cartridges,  bacillus  tetani  in 6 

Blankets,  bacillus  typhi  on 185 

Blood,  bacillus  typhi  in 30 

infection  of,  cause  of  typhoid  fever.  .*: 30 

meningococcus  in 45 

yellow  fever  virus  in 333-334 

Boer  War,  typhoid  fever  from  dust  in 229-230 

flies  in 359-360 

Books,  bacillus  tuberculosis  on 199 

scarlet  fever  from 173 

Boophilus  annulatus  and  cattle  fever 83 

Botryomycosis 306 

Bovine  tuberculosis  bacillus  may  infect  man 293-294 

Bread,  bacillus  diphtheriae  in 22 

Broad  Street  well 266-267,  275 

Brush,  bacillus  diphtherise  on 198 

Bubonic  plague,  see  Plague. 

Butter,  a  source  of  typhoid  fever 292 

bacillus  tuberculosis  in 304-305 

bacillus  typhi  in 12 

Calliphora  erythrocephala 355 

Camps,  bacillary  dysentery  in 141 

filthy  condition  of 138 

typhoid  fever  in . 128-129,  258-559 

Caps  and  gowns  to  prevent  infection . .  ; 176,  232 

Carbolic  acid  in  well  water 274 

Carriers  a  recent  discovery 29 

and  mild  cases,  number  of 91-93 

cause  cattle  fever 83-84 

cerebro-spinal  meningitis 46-53 

cholera 143 

diphtheria 66-71 

glanders 71 


INDEX  375 

Page 

Carriers  cause  malaria 84-86 

nagana 87 

typhoid  fever 36-37 

during  incubation 34 

explain  spread  of  cerebro-spinal  meningitis 50-53 

less  infective  than  the  sick 113 

more  dangerous  than  things 183 

of  amebic  dysentery 87-88,  141 

bacillary  dysentery 43 

cattle  fever 83 

cerebro-spinal  meningitis 44-53 

cholera 39-40 

diphtheria,  importance  of 107-110 

glanders 71 

gonorrhea 74 

influenza 71 

lepra  bacilli 77 

malaria 84-86 

measles 82 

Mediterranean  fever 44 

nagana 87 

paratyphoid  fever 39 

plague 42 

pneumococcus 73-74 

pus  organisms 77-78 

scarlet  fever 80 

sleeping  sickness 86-87 

smallpox 82 

tetanus  bacilli 78 

tubercle  bacilli 75-77 

typhoid  fever 30-38 

among  contacts 33-34 

cannot  be  isolated 110 

danger  from 93 

Cartridges,  bacillus  tetani  in 184 

Celery,  typhoid  fever  caused  by 319 

Cerebro-spinal  meningitis  an  accident  of  infection 53* 

due  to  pneumococcus 53 

Cerebro-spinal  meningitis,  carriers  of 44-53 

explain  spread  of 50-53 

contagiousness  of 51-52 

infection  by  carriers 46-53 

isolation  a  failure  in 53,  104 

path  of  infection 45 

prompt  isolation  in,  a  success 104 

secondary  cases 51-52 

Charbon  symptomatique 4 

Charts,  bacillus  tuberculosis  on 199-200 

Chicken  pox,  air-borne 224 

Children  not  cleanly 148 

Cholera  and  contact ♦ 142-143 

flies 352,  35&-357 

fomites 1 73 


376  INDEX 

Page 

Cholera  caused  by  washing  soiled  linen  in  running  streams 275 

from  betel  nut 143 

carriers 143 

clothing 173 

handling  food 143 

rags 180 

shellfish 314 

soil 25 

unrecognized  cases 16 

water 275-276 

wells 275-276 

not  dust-borne 239-240 

on  shipboard  due  to  infected  water 276 

outbreaks  in  various  places 16 

Cholera,  infection  of  nurses 143 

Cholera  spirillum,  see  Spirillum  cholerse. 

Christmas  presents,  diphtheria  from 173 

Cimex  lectularius,  see  Bedbug. 

Citellus  beecheyi 346 

Clams,  typhoid  fever  from 315 

Clay,  bacillus  diphtheria;  in 191 

Cleanliness,  education  in,  needed 166-167 

municipality  should  encourage 168-169 

Cleanliness  in  school,  teaching  of 167-168 

neglected 164-166 

rare 136-138 

in  children 148 

versus  disinfection 211 

Cloth,  yellow  fever  from 171 

Clothing  as  fomites 174 

Clothing,  bacillus  tuberculosis  on 200 

cholera  from 173 

infection  by,  rare 175-177 

leprosy  in 174 

scarlet  fever  not  from 175 

typhoid  fever  from 177 

typhus  fever  not  from 174-175 

Coat,  bacillus  diphtherise  on 185 

scarlet  fever  from 173 

Cockles,  typhoid  fever  from 315-316 

Cockroaches  and  disease 355 

Colon  bacillus,  see  Bacillus  coli  communis. 

Communion  cups,  bacillus  tuberculosis  in 153 

individual,  adopted 168 

Conductors  not  infected  by  money 182 

Contact  by  drinking  cups 147-148,  150 

chief  mode  of  infection 153-164 

infection  and  fingers 146-147 

infection  less  easy  in  some  diseases  than  in  others ....  145-146 

most  obvious 122 

in  amebic  dysentery 141 

bacillary  dysentery 43,  141-142 

diarrhea 143 


INDEX  377 

Page 

Contact  infection  in  diphtheria 154-160 

cerebro-spinal  meningitis 45-46,  48-49,  52 

cholera 142-143 

gonorrhea 123-125 

influenza 231-232 

measles 157 

Mediterranean  fever 262 

scarlet  fever 154-160 

syphilis 122,  125-127 

tuberculosis 162-163 

typhoid  fever 13,  127-141 

in  civil  life 129-131 

typhoid  fever,  amount  of 135-136 

evidences  of 135 

in  hospitals 156-160 

opportunities  for 137-138 

role  of  privies 138-140 

Spanish  war 128 

why  disregarded 137-139 

uncinariasis 144 

infection,  disregard  of 165-166 

importance  of 164 

opportunities  for 148-150 

Contact,  indirect,  vehicles  for 146-148 

mode  of  infection  between  families 154-156 

with  missed  cases,  importance  of 148-150 

with  well  carriers,  importance  of 149-150 

Contacts,  typhoid  carriers  among 33-34 

diphtheria  carriers  among 61 

Contagiousness,  factors  involved 111-113 

Contagiousness  less  outside  family 112-113 

than  believed 11 1-113 

of  carriers  less  than  that  of  sick 113 

Convalescents,  diphtheria  bacilli  in 56,  57 

dysentery  amebtr  in 88 

dysentery  bacilli  in 43 

cholera'  spirilla  in 39-40 

malarial  parasites  in 84-86 

meningococci  in 46-49 

plague  bacilli  in 42 

pneumococci  in 73 

typhoid  bacilli  in 31,  35 

Cornet,  diphtheria  from 173 

Cotton  goods,  bacillus  pestis  on 186 

( 'otton,  smallpox  from 172 

Cow  dung,  bacillus  pestis  in 19 

('ows,  diphtheria  in 290 

scarlet  fever  said  to  occur  in 289-290 

Crawfish  and  typhoid  fever 318 

('ubicles  for  isolation  in  French  hospitals 156-158 

(yulex,  experiments  with 323 

('ulex  fasciatus  and  yellow  fever 332 

Culex  fatigans  and  dengue 343 


378  INDEX 

Page 

Culex  fatigans  and  filariasis 339 

Culicidcs 328-329 

Culicides,  mosquito  destruction  by 330,  337 

Culture  method  of  diagnosis,  introduction  of 95-96 

Cups,  bacteria  on 150-151 

Dead  animals,  bacillus  typhi  in 8 

Dead  bodies,  spirillum  cholerae  in 15 

Dengue  transmitted  by  mosquitoes 342-343 

Dcrmacenter  andersoni 345 

Diarrhea,  bacteria  which  cause 307 

Diarrhea  due  to  condensed  milk 308-309 

contact 143-307 

dust 230-231 

flies 357-358 

statistical  evidence 361-363 

milk 306-309 

not  always 143 

water 277-278 

Diarrhea,  explosive  outbreaks 309 

nature  of 306-307 

prevention  of 309-310 

relation  of  feeding  to 307-309 

Diphtheria,  atypical 64-66,  91 

chronic 71 

extension  in  dwellings , 155-156 

family  infection 61-62 

not  from  soil 24 

of  extra-corporal  origin 25 

similarity  to  scarlet  fever 78-79 

warning  sign  in 109 

with  recurrent  ear  discharge  causes  infection 70 

Diphtheria  bacillus,  see  Bacillus  diphtheriae. 

carried  to  homes  by  discharged  scarlet  fever  cases ...        70 

carriers,  importance  of 107-110 

isolation  of,  often  impossible 108-110 

cultures  introduced 95-96 

value  of  findings  56-57 

from  carriers 67-71 

Christmas  presents 173 

cornet 173 

drinking  glass 150 

fomites 173-185 

milk 68-69,  289-290 

pitcher 69 

sewer  air 227 

teacher 69 

tools 173 

in  cows 290 

Owatonna,  Minn 102 

Providence 94,  96 

Willard  State  Hospital. 102 

isolation,  duration  in  Providence 101 


INDEX  379 

Pace 

Diphtheria  isolation  in  institutions,  failure  of 101-103 

isolation,  principles  of 107-110 

mild  cases  found  by  cultures 96 

not  air-borne  in  hospitals 227-228 

dust-borne 240 

Disease  rarely  carried  by  physicians 1 75 

Dishes,  bacillus  tuberculosis  from 153 

Disinfection  desirable  at  times 210 

in  Providence 95 

abandoned 206-208 

schools 209 

of  little  value 205-209 

unnecessary  in  certain  diseases 209-210 

versus  cleanliness 211 

Disinfection,  English  views  on 208-209 

French  views  on 208 

objections  to 210-211 

Dog  drinks  from  the  drinking  glass  on  train 148 

Drainage,  mosquito  destruction  by 330 

Dresses,  bacillus  tuberculosis  on 152 

Drinking  cups,  contact  by 147-148 

Drinking  glass,  bacillus  diphtheria;  on 150 

common,  abolished 168 

Droplet  infection 245-248 

Droplets,  bacillus  influenzae  in 248 

bacillus  lepra?  in 247 

bacillus  prodigiosus  in 245-247 

bacillus  tuberculosis  in 245-246 

pneumococcus  in 248 

streptococcus  salivarius  in 247 

Droplets  versus  dust 253-255 

Drying,  effect  upon  bacteria 189-190,  23S-239 

resistance  of  bacillus  diphtherias  to 191-240 

bacillus  pestis  to 193-194  240-241 

bacillus  dy.senteria?  to 192 

bacillus  influenza"  to 196 

bacillus  tuberculosis  to 192-193,  199-200,  241 

bacillus  typhi  to 190-191  240 

gonococcus  to 197 

meningococcus  to 196-197 

micrococcus  of  Mediterranean  fever  to 191 

pneumococcus  to 196 

protozoa  to 200 

pus-forming  bacteria  to 194-195 

smallpox  virus  to 202 

spirillum  cholerie  to 195-196,  200,  241-242 

spirochete  of  syphilis  to 197 

spores  to 190 

vaccine  virus  to 200-202 

Dust,"  anthrax  spores  in 185 

bacillus  coli  communis  in 244 

bacillus  diphtheria:  in 240  244 

bacillus  pestis  in 240-243 


380  INDEX 

Page 

Dust,  bacillus  tuberculosis  in   242-243 

bacillus  typhi  in 240 

danger  from  slight 244-245 

micrococcus  melitensis  in 17,  250 

meningococcus  in 239-240,  243 

pneumococcus  in 24^244 

pus  organisms  in 244 

Dust  infection 238 

versus  droplets 253-255 

Dust-borne  disease 238-240 

disease,  anthrax 235-236 

diarrhea 230-231 

influenza •  231 

Mediterranean  fever 262 

poliomyelitis 232 

tuberculosis 238,  241-243,  251-261 

typhoid  fever 229-230 

Dwellings,  extension  of  diphtheria  in 155-156 

scarlet  fever  extension  in 154-155 

Dysentery,  see  Bacillary  dysentery. 

amebic 87,  141 

amebic,  due  to  chronic  carriers 141 

infection  from  bedpan 141 

produced  in  men  by  amebaj  grown  in  culture.       20 

monkeys  by  amebse 20 

transmitted  by  contact 141 

infection  by  water 276-277 

Dysentery  bacillus,  see  Bacillus  dysenteria;. 

due  to  files 353,  357 

Ear  discharge  causes  diphtheria 70 

East  coast  cattle  fever 84 

Elephantiasis 339 

Endemic  diseases 25-26 

English  hospitals 97-100 

isolation  in 158-160 

Entameba  coli  and  entameba  histolytica,  distinction  between.  ...       88 
Erysipelas  from  rags 180 

Family,  carriers  in,  cerebro-spinal  meningitis 47 

diphtheria  61 

infection  of,  in  house 24,  154-156 

isolation  in 118-119 

typhoid  fever  by  contact  in 134 

Feces,  bacillus  dysenterise  in 20 

paratyphi  in 12 

typhi  in 8,  31,  32,  36 

typhi  in,  persistence  of 31-32 

intermittency  of 36 

hookworms  in 145 

spirillum  cholerse  in 15 

Filaria  bancrofti 338 

Filariasis  and  mosquitoes 338-339 


INDEX  381 

Pajie 

Filth  theory  of  disease 23 

Filtration  of  water 282 

reduces  typhoid  fever 271 

Fingers  and  contact  infection 146-147 

Fish,  infection  by  fried 318 

Fishermen,  influenza  among 231 

Fleas  and  anthrax 350 

plague 19,  262-263,  346-349 

Fleas,  bacillus  pestis  in 194,  347-348 

Flies  a  nuisance 360 

and  anthrax 3,  356 

cholera 352,  356-357 

diarrhea 357-358 

diarrhea,  statistical  evidence 361-363 

dysentery 353,  357 

Egyptian  ophthalmia 356 

plague 356 

typhoid  fever, 127-129,  140-141,  358-360 

statistical  evidence 363-365 

carry  fecal  bacteria 354 

germs 351-354,  356 

lime  from  privies 354-355 

Flies,  bacillus  tuberculosis  in 353-354 

control  of 366-367 

habits  Ijring  them  in  contact  with  excrement 360-361 

infected,  in  typhoid  houses 352 

local  variation  in  distribution 365 

species  in  houses 355 

tuberculosis  due  to 353,  356-357 

Flock  cough  from  rags 180 

Floors,  bacillus  pestis  not  on 193 

tetani  in  dirt  of 197 

Fly  specks,  bacillus  tuberculosis  in 353 

Fomites:  Bagging 171 

Ballast 171 

Barbers'  utensils 126 

Barracks 48,  174 

Bedding 126,  172 

Blankets 185 

Books 173,  199 

Bru^ 198 

Cartridges 6,  184 

Charts 199,  200 

Christmas  presents 173 

Clay 191 

Cloth ■ 171 

Clothing 127,  173-174,  177,  200 

Coat 173,  185 

Communion  cups 153 

CJornet 173 

Cotton 172 

Cotton  goods 186 

Cups 150,  151 


382  INDEX 

Page 

Fomites:  Dentists'  tools 126 

Drinking  glass 126, 147-148,  150, 153, 198 

Floors 193,  197 

Furniture 199 

Gelatine 6,  184 

Glass  blowers'  tubes 126 

Grain 171 

Hair 173,  184,  185 

Handkerchief 126,  192,  198,  243 

Hides 184,  185 

House,  see  Room 

Lamp  wick 6,  184 

Letters 173 

Linen,  soiled 172,  198,  133 

Lumber 172 

Mattress 171 

Merchandise 171 

Mirror 198 

Money 126,  181,  182 

Napkin  rings 158 

Nursing  bottles 126 

Oyster  buckets 171 

Pencils 126,  150,  151,  191 

Pins 126 

Pitcher 69 

Rags 127,  180 

Railway  carriages 242 

Roller  towel 168 

Room 172,  174,  177-180, 191,  193,  199,  242,  244 

Rugs 181 

Shoes 176,  198 

Spirometer 199 

Spoons,  etc 126 

String 126 

Surgeons'  instruments 126 

Telephones 153,  199 

Thermometer 132 

Tools 173 

Toys 198 

Tramcars 242 

Wind  instruments 126 

Wool 184,  185 

Fomites  and  anthrax 184-185 

cholera 173 

diphtheria 173,  185 

plague,  experiments  in  India  ; 204-205 

observations  in  Sydney 203-204 

scarlet  fever 172-173 

smallpox 172 

tetanus 183-184 

tuberculosis,  lack  of  experiments 205 

typhoid  fever 185 


INDEX  383 

Fomites  and  yellow  fever 171-172,  334 

fever,  experiments  in  Havana 203 

thought  important 95 

Fomites,  bacillus  diphtheria?  on 198-199 

bacillus  tuberculosis  on 199-200 

bacteria  of  suppuration  on 21 

bacteria  on 197-198 

clothing  as, 174 

conclusions  concerning 211-212 

definition  of  term 170-171 

evidence  of  infection  by,  unsatisfactory 182-183 

reasons  for  belief  in 186-187 

Fomites  infection,  bacteriological  evidence 188-189 

evidence  against 187-188 

few  instances  of 186 

Food  infection  and  cholera 143 

tuberculosis 312-313 

typhoid  fever 127-128,  304,  314-319 

poisonings 31 1-312 

Food,  handling  by  contacts 120-121 

spirillum  cholera?  in 16 

Foot-and-mouth  disease  and  milk 306 

French  hospitals 156-158 

French  hospitals,  "Antisepsie  medicale"  in 156 

cubicles  for  isolation  in 156-158 

screens  for  isolation  in 156-158 

Furniture,  bacillus  diphtheria?  on 199 

Gelatine,  bacillus  tetani  in 6,  184 

Glanders,  carriers  of 71 

Glands,  bacteria  of  suppuration  in 21 

cervical  and  mesenteric,  bacillus  tuberculosis  in 161 

Glass,  bacillus  diphtheria?  on 198 

tuberculosis  on 153 

contact  infection  by  drinking  from 147-148 

Glossina  morsitans 87 

palpalis 86,  339-341 

Goats  and  Mediterranean  fever 17,  44,  305 

Gonococcus,  not  saprophytic 22 

resistance  to  drying 197 

Gonorrhea,  air-borne  infection  not  possible 124-125 

infection  by  fomites  impossible 124-125 

latency  of 74-75 

persistence  of 74-75 

Gonorrhea  believed  to  be  spread  by  contact 122-127 

carried  by  nurses 124-125 

in  Babies'  Hospital 123-124 

not  dust-borne 239 

Gown  and  cap  for  physicians  and  nurses  in  contagious  cases 176 

Grain,  yellow  fovcr  from 171 

Ground  squirrels  and  i)laguc 346 

Guinea  pigs,  bacillus  pestis  in 42 


384  INDEX 

Page 

Hair,  anthrax  spores  in :  184-185 

scarlet  fever  from ■ 173 

Handkerchief,  bacillus  diphtherise  on 198 

tuberculosis  on 192,  243 

Hands,  bacillus  coli  communis  on 137 

tuberculosis  on .  .  151-152 

pus  bacteria  on 150-152 

Hands  should  be  washed 137-138 

Hides,  anthrax  spores  in 184-185 

Holy  water,  bacillus  diphtherise  in 150 

Homalomyia  canicularis 355 

Home  isolation  effective 118 

Hookworms,  see  Uncinaria,  Anchylostoma 144-145 

enter  through  skin 145 

grow  in  soil 144 

in  feces 145 

Hospital,  isolation  in 119 

Hospital  isolation,  failure  of 97-100 

Hospitals,  bacillary  dysentery  in 141-142 

contact  infection  in 156-160 

diphtheria  not  air-borne  in 227-228 

scarlet  fever,  not  air-borne  from 226-227 

smallpox,  air-borne  infection  from 214-224 

typhoid  fever  by  contact  in 131-132 

value  of 118 

Hospitals  in  America 100-103 

England 97-100 

France 156-158 

House,  infection  from  family  to  family 24 

of,  cause  of  scarlet  fever 172-173 

tuberculosis  infection  in 163,  178-180 

Houses,  species  of  flies  in 355 

Ice,  bacillus  typhi  in 10,  269 

infection  by 283-285 

Ice  cream,  a  source  of  disease 292 

Incubation  stage  infective 34 

Infection,  former  theories  of 1 

Infection  not  so  easy  as  believed 149-150 

Influenza,  atypical  cases 71 

Influenza  among  fishermen 231 

lighthouse  keepers 231 

bacillus,  see  Bacillus  influenza} 

from  rags 180 

not  air-borne    231-232 

carried  across  Atlantic 231 

dust-borne 231,  239 

spread  only  by  contact 231-232 

Inhalation  of  bacteria 254-255 

Insect-borne  disease  usually  due  to  protozoa 320-321 

Insects,  first  proof  of  transmission  of  disease  by 321-322 

infection  by,  importance  of  subject 320 

summary 367 


INDEX  385 

Page 
Insects,  Texas  cattle  fever  first  disease  proved  to  be  carried  by . .  321-322 

Insects  as  biological  and  mechanical  carriers 320-322 

carry  germs  on  bodies 351 

Isolation,  causes  of  failure 105-107 

duration  of 118-120 

value  of 109-110 

Isolation  a  failure  in  cerebro-spinal  meningitis 104 

measles i03-104 

smallpox 105 

Isolation  effective  if  prompt 104,  115-116 

in  Michigan 1 14-1 16 

rare  diseases 116-117 

hospitals,  failure  of 97-100 

in  American  cities 100-103 

English  hospitals 158-160 

family 118-119 

family,  effective 118 

hospital 119 

Monsall  Hospital 158-160 

Providence 94,  1 18 

villages 113-116 

not  effective  in  extensive  outbreaks 116 

to  be  too  strict 109-110 

of  cerebro-spinal  meningitis 104 

diphtheria 94,  95-97,  101,  107,  114 

diphtheria,  duration  in  Providence 101 

malaria 328 

measles 103,  114 

plague 348 

rare  diseases 114 

scarlet  fever 94,  97,  114 

school  children 120 

sleeping  sickness 341 

smallpox 97,  105,  114 

typhoid  fever 110,  114 

wage  earners 110,  120-121 

yellow  fever 336 

should  vary 113 

too  rigorous 110-111 

useless  if  many  carriers 117 

Jews  do  not  eat  shellfish 316 

Kala-azar  and  insects 342 

transmitted  by  bedbugs 342 

Kala-azar,  protozoan  discovered 342 

Kissing  means  of  spreading  syphilis 126 

spread  of  tuberculosis 160-161 

Laboratory  infection,  bacillary  dysentery 141-142 

typhoid  fever 133 

Laboratory,  tuberculosis  infection  in 258-259 

Lamblia 83 


386  INDEX 

Page 

Lampwick,  bacillus  tetani  on 6, 184 

Latency  of  infection  common 78 

Laundress  contracts  smallpox 172 

typhoid  fever 133 

Laundries  and  disease 176-177 

tuberculosis 177 

Leishmania  donovani 342 

Leprosy,  bacilli  remain  latent 77 

isolation  of 114 

Leprosy  in  clothing 174 

Letters,  scarlet  fever  from 173 

Lice  and  relapsing  fever 345 

Light,  bacillus  tuberculosis  perishes  in 192-193 

Lighthouse  keepers,  influenza  among 231 

Linen,  soiled,  smallpox  from 172 

typhoid  fever  from 133,  177 

Lockjaw,  see  Tetanus. 

Lucilia  coesar 355 

Lumber,  smallpox  from 172 

" Lung  Blocks"  in  New  York 178-180 

Lupus  due  to  inoculation  with  saliva 161 

Malaria,  an  endemic  disease 25-26 

anointing  the  skin  in 329 

clearing  of  space  about  dwellings 329 

discovery  of  insect  transmission 322-323 

experiments  on  infection  of  human  beings 323 

isolation  sometimes  necessary 328 

killing  of  mosquitoes  in  houses 328 

latency  of 84-86 

latency  of,  explanation 85-86 

in  children 85-86 

latency,  percentage  of 85-86 

mosquito  sole  carrier  of 323-325 

screening  of  patients 328 

success  of  mosquito  destruction 330-331 

ways  of  prevention 326-330 

Malaria  and  insects 322-332 

water 324 

not  air-borne 324 

due  to  soil  infection 26 

from  water 278-279 

on  ship  Argo 278 

Malta,  Mediterranean  fever  exterminated  at 44 

Malta  fever,  see  Mediterranean  fever. 

Mattress,  yellow  fever  from 171 

Measles  an  air-borne  disease 232 

Measles,  carriers  of 82 

disinfection  after 208 

isolation  in,  a  failure 103-104 

not  from  soil 24 

number  attacked 82 

per  cent  of  children  attacked 103 


INDEX  387 

Page 

Meat  and  tuberculosis 312-313 

Meat,  infection  by 311-314 

inspection,  federal  control  of 313-314 

Mechanical  carriers  distinguished  from  biological  carriers 346 

Mediterranean  fever  an  endemic  disease 17 

and  contact  infection 262 

dust 262 

goats 17,  44,  305 

caused  by  milk  from  infected  goats 17,  305 

Mediterranean  fever,  experiments  in  infection  by  air 261-262 

exterminated  at  Malta 44 

goats  carriers  of 44 

human  carriers  of 44 

in  United  States 305 

micrococcus  of,  resistance  to  drying 191 

on  a  steamship 44 

spread  by  urine 18 

Membrane,  bacillus  diphtheriae  in 198 

Meningitis,  cerebro-spinal,  see  Cerebro-spinal  meningitis. 

Meningococcus  causes  rhinitis 45 

found  intermittently 48 

only  near  sick 49 

in  air 49 

contacts 45-46,  48-49,  52 

dust 239-240,  243 

families 47-52 

normal  nose 45 

nose  in  sickness 44 

Meningococcus,  infection  in  barracks 48 

not  saprophytic 22 

persistence  of  infection 46-47 

resistance  to  drying 196-197 

Merchandise,  yellow  fever  from 171 

Michigan,  isolation  effective  in 114-116 

Micrococcus  albus 20 

aureus 20 

citreus 20 

nelitensis,  discovery  and  study  of 17 

in  dust 17,250 

resistance  to  drying 191 

saprophytic  existence  of 17 

meningitidis,  see  Memingococcus. 
pneumoniae,  see  Pneumococcus. 

Mild  cases  of  infectious  disease  not  recognized 92-93 

Milk,  bacillus  diphtheria;  in 21-22 

dysenteriaj  in 11 

tuberculosis  in 295-296 

typhi  in 11-13 

classification  of 303 

condensed  and  diarrhea 308-309 

diarrhea  from 306-309 

diphtheria  from 68-69,  289-290 

foot-and-mouth  disease  from 306 


388  INDEX 

Page 

Milk,  handling  by  contacts 120-121 

increase  of  bacillus  typhi  in 13 

infection  by  water 273 

from  human  sources 290-291 

Mediterranean  fever  from 305 

mode  of  infection  of 290-291 

pasteurization  of 291-292 

protection  against  tuberculosis  from 302-303 

of 291-292 

rabies  from 306 

scarlet  fever  from 289-290 

spirillum  cholerae  in 15 

sterilization  of  vessels 291 

tuberculous,  consumed  by  children 297-300 

typhoid  fever  from 37,  286-288 

tuberculosis  from,    294-302 

tuberculosis  from,  amount  of 296-302 

epidemiological  evidence 301-302 

instances  of 300 

Milk  and  disease 285-310 

outbreaks,  characteristics 285-286 

few  in  large  cities 287-288 

frequency  of 286-287 

source  of  infection 289-290 

Miners,  typhoid  fever  among 140 

Minnesota,  smallpox  isolation  abandoned  in 105 

Mirror,  bacillus  diphtheriae  on 198 

Missed  cases  a  recent  discovery 29 

Moist  surfaces,  bacteria  not  given  off  from 237-238 

Money  and  disease 181-182 

Money,  bacteria  on 181-182 

Monkeys,  dysentery  in 20 

Monsall  Hospital,  isolation  in 158-160 

Montana,  smallpox  isolation  abandoned  in 105 

Mosquito  destruction  by  culicides 330,  337 

drainage 330 

oiling 330 

prevention 329-33 

Mosquitoes  and  dengue 342-343 

filariasis 338-339 

malaria 322-323 

malaria,  conditions  for  carrying 325,  326 

yellow  fever 332-338 

yellow  fever,  destruction  of 337 

habits 335 

Mosquitoes,  destruction  of,  in  malarious  houses 328 

habits  of 325 

species  which  carry  malaria 322-323,  325 

success  of  measures  for  extermination 330-331 

transportation  of 335 

Mouth,  bacillus  tuberculosis  in 75-76,  151 

bacteria  in 150 

pneumococcus  in 73-74 


INDEX  389 

Page 

Mucous  surfaces,  bacteria  of  suppuration  on 20 

Mud  dumped  near  intake  cause  of  typhoid  fever 270 

Municipal  versus  personal  prevention 166 

Murium  typhi,  bacilli  of,  carried  by  ants 355 

Musca  domestica 355 

Muscina  stabulans 355 

Mussels,  infection  by 315-317 

Myzomyia  ludlowii 325 

Nagana 87 

North  Boston  well 267 

Nose,  bacillus  tuberculosis  in 75-76,  151,  249 

meningococcus  in,  in  sickness 44 

in  normal 45 

tuberculosis  of 162 

Nurses,  gown  and  cap  for,  in  contagious  cases 176 

typhoid  fever  among 131-132 

Nurses  infect  patients  with  typhoid  fever 132 

Oiling,  mosquito  destruction  by 330 

Ornithodorus  moul)ata 344 

Ophthalmia,  Egyptian,  carried  by  flies 356 

Opsonic  index  in  typhoid  carriers 35 

Otitis,  bacillus  diphtherias  in 66-67 

Owatonna,  Minn.,  diphtheria  in 102 

Oyster  buckets,  j^ellow  fever  from •    171 

Oysters,  bacillus  typhi  in 10 

"fattening"  of 317 

infection  by 314-318 

Pail-closets  cause  typhoid  fever 139-140 

Paratyphoid  bacilli,  see  Bacillus  paratyphi. 

Pencils,  bacillus  diphtheriae  on 151,  191 

bacteria  on 150-151 

Personal  versus  municipal  prevention 166 

Persons,  not  things,  are  dangerous 183 

Phy.sicians,  gown  and  cap  for,  in  contagious  cases 176 

Physicians  rarely  carry  disease 175 

Pigment  to  lungs  from  stomach 256 

Piroplasma  bigeminum 83,  321-322 

Placards  for  contagious  diseases 109 

Plague  and  bedbugs 347 

fleas 19,  262-263,  346-349 

fleas,  epidemiological  evidence 347-348 

experimental  work 347-348 

fliea 356 

fomitcs,  experiments  in  India 204-205 

oljsorvations  in  Sydney 203-204 

ground  squirrels 346 

other  rodents 346-349 

rats 19,  42,  346-349 

rugs 181 

bacillus,  see  Bacillus  pestis. 


390  INDEX 

Page 

Plague  not  dust-borne 239-240 

Plague,  atypical  human 42 

rat 41 

chronic  in  rats 41 

experiments  in  infection  by  air 262-263 

isolation  of 348-349 

Plasmodium 84,  324-325 

Pneumococcus  cause  of  meningitis 53 

in  air 250 

convalescents 73 

droplets 248 

dust 243-244 

normal  mouths 73-74 

may  be  air-borne 239 

not  dust-borne 240 

Pneumococcus,  not  saprophytic 22 

persistence  of 73 

resistance  to  drying 196 

virulence  of,  in  carriers 73-74 

Poisoning  by  food 311-312 

Poliomyelitis  a  dust-borne  disease 232 

Privies  and  water-closets  usually  filthy 137-138 

encourage  uncleanliness 140,  169 

infect  water  supplies 270 

Privies,  removal  of,  causes  decrease  of  typhoid  fever 139-141 

typhoid  fever  from. 127-128,  137-141 

Privy  vaults,  bacillus  typhi  in 8 

Prosedemic  infection,  typhoid  fever  by 130 

Proteosoma  in  birds 323 

Protozoa,  difficult  to  cultivate 23 

not  saprophytic 22 

resistance  to  drying 200 

Protozoan  diseases,  latency  in 82-83 

Psocidae  and  disease 355-356 

Pulex  irritans 347 

Purification  of  water 282-283 

Pus  bacteria 20 

in  air 249-250 

dust 244 

glands 21 

schoolrooms 244 

skin  and  mucous  surfaces 20 

tonsils 20 

water 21 

may  be  dust-borne 239-240 

on  fomites 21 

Pus  bacteria,  distribution  of 198 

resistance  to  drying 194-195 

saprophytic  existence  of 20-21 

Quarantine  and  sleeping  sickness 341 

yellow  fever 336 

oflBcers  take  the  temperature  of  passengers 89 

Quinia  prevents  malaria 326-328 


INDEX  391 

Page 

Rabies  from  milk 306 

Rags  and  disease 180-181 

Rags,  ciiolera  from 180 

erysipelas  from 180 

flock  cough  from 180 

influenza  from 180 

scarlet  fever  from 180 

septicemia  from 180 

smallpox  from 180-181 

typhoid  fever  from 180 

Railway  carriages,  bacillus  tuberculosis  in 242 

Rat-proofing  of  buildings 349 

Rats  and  plague 19,  41-42,  34&-349 

Rats,  carriers  of  plague 42 

chronic  plague  in 41 

destruction  of 349 

Relapsing  fever  and  bedbugs 344-345 

lice 345 

ticks. . . 343-344 

Rhinitis,  bacillus  diphtheria;  in 66-67 

Rhinitis  caused  by  meningococcus 45 

Rhode  Island,  death  rate  from  typhoid  fever 14 

Rice,  spirillum  cholera;  in 16 

Rocky  Mountain  fever  and  ticks 345 

Rodents,  plague  derived  from 346-349 

Roller  towel  should  be  abolished 168 

Room,  bacillus  diphtheria;  in 191,  199 

tuberculosis  in 193 

Room  infection  cause  of  typhoid  fever  in  barracks 174 

Rooms,  infection  of 163,  172-173,  177-180 

Rugs  and  plague 181 

Saliva,  bacteria  in 150 

inoculation  with,  cause  of  lupus 161 

transfer  of 147 

Saliva  vehicle  of  infection 146-148 

Sarcophaga 355 

Scarlet  fever,  air-borne 224-227 

air-borne,  out  of  doors 226-227 

atypical 79-80 

atypical,  frequency  of 80 

extension  in  dwellings 154-155 

not  from  soil 24 

virulence  varies  in 98 

Scarlet  fever  and  fomites 172-173 

books 173 

clothing 175 

coat : 173 

house  infection 172-173 

letters 173 

milk 289-290 

rags 180 

hospital  temporarily  closed  in  Leicester 99 


392  INDEX 

Page 

Scarlet  fever  hospitals  in  England 97-100 

in  Providence 94 

like  diphtheria 78-79 

not  air-borne  from  hospitals 226-227 

said  to  occur  in  cows 289-290 

Scenopinus  fenestralis 355 

School  children,  isolation  of 120 

disinfection 209 

School,  teaching  cleanhness  in 167-168 

Schoolrooms,  bacillus  coli  communis  in 244 

pus  organisms  in 244 

Screening  of  cases  of  malaria 328 

yellow  fever 336-337 

for  protection  against  malaria 328 

Screens  for  isolation  in  French  hospitals 156-158 

Sedgwick,  typhoid  fever  outbreak  in  Bondville,  Mass 127 

Seltzer  water,  bacillus  typhi  in 10 

Septic  infection  and  insects 350-351 

tank  effluent,  bacillus  typhi  in 8 

Septicemia  from  rags 180 

Sewage,  bacillus  typhi  in 8 

Sewer  air  and  bacteria 234-235 

diphtheria 227 

typhoid  fever 228-229 

Sewer  air,  bacillus  prodigiosus  in 234 

bacillus  typhi  in 234 

infection  by 247,  249 

Sex  of  smallpox  cases 221 

Sheet  hung  before  door  to  prevent  infection 232 

Shellfish,  infection  by 314-318 

Shipboard,  influenza  on 231 

malaria  on 278 

typhoid  fever  by  contact  on 134 

Ships  for  smallpox  hospitals 216-217 

Shoes  as  carriers  of  infection 176 

Shoes,  bacillus  diphtheria  on 198 

Sidewalks,  virulent  bacilli  tuberculosis  on 152 

Skin,  bacteria  of  suppuration  in 20 

hookworms  enter  through 145 

Sleeping  sickness,  an  endemic  disease 26 

atoxyl  to  prevent 342 

discovery  of  trypanosome 339-340 

is  it  carried  mechanically? 340-341 

modes  of  transmission 339-341 

not  due  to  soil  infection 26 

per  cent  of  carriers 86-87 

persistence  of  infection 86-87 

prevention  of 341-342 

quarantine 341 

Sleeping  sickness  and  tsetse  flies 339-341 

in  lower  animals 340 

Smallpox,  air-borne,  conclusions 223-224 

evidence  against 220-223 


INDEX  393 

Page 

Smallpox,  air-borne,  objections  to  theory 219-220 

sex  of  cases 221 

air-borne  infection  of,  denied 217-224 

in  United  States 218-219 

atypical  cases 91 

isolation  in,  often  a  failure 105 

mild  cases  of 81-82 

not  from  soil 24 

Smallpox  and  fomites 172 

rags 180-181 

carriers 82 

hospital  ships 216-217 

virus,  resistance  to  drying 202 

Soft  drinks,  bacillus  tjphi  in 10 

Soil,  ameba;  dj-sentoria'  in 20 

bacillus  diphtherite  in 22,  24 

dysenteriaj  in 19 

pestis  in 18 

tetani  in 197 

typhi  in 7 

hookworms  grow  in 144 

melitensis  micrococcus  in-. 17 

not  infected  with  cattle  fever 26 

malaria 26 

measles 24 

scarlet  fever 24 

sleeping  sickness 26 

smallpox 24 

Texas  cattle  fever 26 

yellow  fever 26 

spirillum  cholera?  in 15,  16 

Soil  infection,  cholera  from 25 

typhoid  fever  from 25 

Soil  infection  in  common  diseases 24 

Spanish-American  War,  typhoid  fever  in 13,  38 

from  dust  in 229-230 

Spirillum  cholera?  found  in  water 276 

grow  only  in  human  body 16 

in  convalescents 39-40 

cooked  food 16 

dead  bodies 15 

feces 15 

healthy  persons 40 

milk 15 

soil 15,16 

water 15 

Spirillum  cholera^,  resistance  to  drying 195-196,  200,  241-242 

saprophytic  existence  of 15 

Spirocheta  carteri 345 

duttoni 344 

Spirochete  of  syphilis,  latency  of 87 

not  saprophytic 22 

resistance  to  drying 197 


394  INDEX 

Page 

Spirometer,  bacillus  diphtheriiE  not  on  199 

tuberculosis  not  on  153 

Spitting  should  be  forbidden 169 

Spores  may  be  dust-borne 240 

Spores,  resistance  to  drying 190 

Springs  as  sources  of  infection 274 

Sputum,  bacillus  pestis  in 42 

Squirrels,  see  Ground  squirrels  (Citellus  beecheyi). 

Stamp  out  disease,  failure  to 93-94 

Steogmyia  calopus 332,  335 

Sterilization  of  municipal  water  supplies 283 

Stomach,  bacillus  tuberculosis  may  pass  to  lungs  from 255-258 

Stomoxys  calcitrans 355 

Storage  of  water 282 

Street  dust,  bacilli  tuberculosis  not  found  in 242 

Streptococcus  enteritidis,  cause  of  diarrhea 307 

may  be  air-borne 239 

pyogenes 20 

salivarius  in  droplets 247 

Suppuration,  bacteria  of,  in  healthy  organs 77-78 

latency  of  bacteria  of 77-78 

Suppuration  result  of  infection  by  bacteria 20 

Surgery,  air-borne  infection  in 233-234 

Swine  infected  by  bacillus  tuberculosis  through  the  tonsils.  .  . .  161-162 

plague  bacilli  in  air 250 

Syphilis,  air-borne  infection  not  possible 125 

articles  infected  with 126-127 

believed  to  be  spread  bj'  contact 122-127 

droplet  infection  in 125 

fomites  infection  in,  not  important 127 

infection  by  non-sexual  contact 126-127 

kissing 126 

sexual  act  chief  mode  of  infection 126 

spirochete  of,  see  Spirochete  of  syphilis. 

Syphilis  infection  not  persistent 126-127 

spread  solely  by  contact 125-126 

Tabanus  lineola 3 

Teacher  caused  diphtheria 69 

contracts  diphtheria  from  pupil 70 

Telephones,  bacillus  diphtherise  not  on 199 

tuberculosis  on 153 

Tetanus  and  fomites 183-184 

bacillus,  see  Bacillus  tetani. 

from  lamp  wick  used  for  tying  umbilical  cord 5,  184 

in  Red  Bank,  N.J 5 

on  Long  Island 5 

Tetanus,  decrease  of,  in  Havana 184 

Texas  cattle  fever,  an  endemic  disease 26 

persistence  in  blood 84 

fever  carried  by  tick 83-84 

first  disease  proved  to  be  carried  by  insects. 32 1-322 
not  due  to  soil  infection 26 


INDEX  395 

Page 

Thermometer  transfers  bacillus  typhi 132 

Things  not  dangerous  as  persons 183 

Ticks  and  East  Coast  or  African  cattle  fever 84 

relapsing  fev' er 343-344 

Rocky  Mountain  fever 345 

Texas  cattle  fever 83-84,  321-322 

Tidal  mud,  bacillus  typhi  in 8 

Tongue,  bacillus  tuberculosis  on 161 

Tonsils,  bacillus  tuberculosis  in 161-162 

bacteria  of  suppuration  in 20 

tuberculosis  infection  through 256 

of 162 

Tools,  diphtheria  from 173 

Toys,  bacillus  diphtheria  on 198 

Tramcars,  bacillus  tuberculosis  in 242 

Treasurer  of  United  States,  investigation  of  money  as  carrier  of 

disease  by 182 

Treponema  pallida,  life  of,  short 125 

Trier,  typhoid  fever  in 13,  39 

Trypanosoma  gambiense 86,  339-341 

brucei 87 

Tsetse  flies  and  sleeping  sickness 86,  339-341 

nagana 86 

Tuberculosis  and  fomites,  lack  of  experiments 205 

laundries 177 

meat 312-313 

bacillus,  see  Bacillus  tuberculosis. 

from  flies 353,  356-357 

house  infection 178-180 

milk 294-308 

milk,  amount  of 296-302 

epidemiological  evidence 301-302 

instances  of 300 

protection  against 302-303 

water 279-280 

infection  by  air 152,  160-161 

in  animals  through  mouth  and  pharynx.  162,  256 

laboratory 258-259 

alimentary  tract 161-162 

infection,  experiments  under  natural  conditions.  .259-261 

unnatural  conditions  of  experiment 258 

of  the  nose 162 

tonsils 162 

spread  by  animals  licking  one  another 162 

kissing 160-161 

through  ton.sils 162,  256 

Tuberculosis,  bovine,  eradication  of 304 

contact  infection  in 162-163 

experiments  concerning  air-borne  infection 251-261 

feeding  experiments 294-295 

human  and  bovine  reciprocally  infective 292-293 

infection  by  du.st  riuestioned 252-253 

stomach 255-258 


396  INDEX 

Page 

Tuberculosis,  infection  by,  in  the  home 163 

mode  of  infection,  evidence  from  pathology 163 

proportion  of  human  and  bovine  types  of  bacillus .  300-301 

Tuberculous  milk  consumed  by  children 297-300 

Typhoid  bacillus,  see  Bacillus  typhi. 

carrier  at  Bristol,  Eng 37-38 

carriers 14,  30-39, 138 

among  contacts 33-34 

the  public 35-36 

cannot  be  isolated 110 

cause  disease 36-37 

carriers,  infective  during  incubation  stage 34 

opsonic  index  in 35 

or  mild  cases,  in  Spanish  War 38 

percentage  of 34-35 

feces  in  yard 128,  131,  140 

fever  among  nurses 131-132 

and  high  temperature 365-366 

believed  to  be  an  intestinal  disease 136 

by  bathing 274-275 

contact 13,  37,  127-141 

in  an  almshouse 133 

hospitals 131-132 

the  family 134 

civillife 129-131 

South  Africa 129 

Spanish  War 128-129 

on  shipboard 134 

food  infection. 127-128 

prosedemic  infection 130 

decreases  with  removal  of  privies 139-141 

from  bedbugs 351 

celery 319 

clothing 177 

crawfish 318 

dust 229-230 

flies 127-129,  140-141  358-360 

flies,  statistical  evidence 363-365 

fomites 185 

handling  typhoid  cultures 133 

infected  bedding 133 

milk 37,  288-289 

mud  dumped  near  intake 270 

pail  closets 139-140 

privies 127-128,  137-141 

rags 180 

sewer  air 228-229 

shellfish. 314-318 

soil  infection 25 

soiled  linen 177 

springs 274 

thermometer 132 

unrecognized  cases 91 


INDEX  397 

Pace 

Typhoid  fever  from  water 267-275 

watercress 318-319 

wind  blowing  sewage  to  water  works 270 

houses,  infected  flies  in 352 

in  barracks  due  to  room  infection 174 

mines 140 

soldiers'   home   due   to  contact   infection   from 

physician 133 

Spanish  War 13,  38 

Trier 13 

waitress  due  to  contact  infection 133 

infection  stopped  by  strict  cleanliness 132 

less  with  water  closets 139-140 

not  dust-borne 239-240 

outbreaks  continued  by  contact  infection 130-131 

in  Providence,  R.  I 14 

prevalent  in  country 131 

spread  among  patients  bj'  nurses 132 

by  kitchen  help 133 

by  waitress 133 

"Typhoid  Mary" 37 

Typhoid  fever,  an  infection  of  the  blood 30 

atypical 38-39 

causes  of  excess  in  cities 271 

contact  outbreaks  in  cities 130-131 

contracted  by  laundress  from  soiled  linen 133 

death  rate  in  Rhode  Island 14 

filthy  habits  cause  of 128,  131,  140 

mild  cases  in  Panama 38-39 

Trier 39 

number  of  carriers 138 

Typhus  fever  not  from  clothing 174-175 

Typhus  fever,  not  of  extra-corporal  origin 25 

Uncinaria,  see  Hookworms,  Anchylostoma. 

Uncinaria  americana 144 

due  chiefly  to  contact 144-145 

Urine,  bacillus  typhi  in 31 

cause  of  Mediterranean  fever 18 

Vaccine,  resistance  to  drying 201-202 

transport  across  ocean 200-202 

Vaginitis  in  Babies'  Hospital 123-124 

Vegetables,  ameba;  dysenteria;  on 20 

Venereal  diseases,  see  Gonorrhea  ;  Syphilis. 

Wage  earners,  isolation  of 110,  120-121 

Waitress,  typhoid  fever  spread  by 133 

Warning  sign  in  diphtheria 109 

Washing  soiled  linen  in  running  streams  cause  of  cholera 275 

Water  and  cholera 275-276 

diarrhea 277-278 

dysentery 276-277 


398  INDEX 

Page 

Water  and  malaria 278-279,  324 

tuberculosis 279-280 

typhoid  lever 267-275 

worms 280 

yellow  fever 279 

closets,  typhoid  fever  less  with 139-140 

outbreaks,  characteristics 268-269 

supplies,  infection  of 14 

Water,  bacillus  tj^phi  in 9,  269 

recovered  from 269 

bacteria  of  suppuration  in 21 

Water,  filtration  of 282 

infection  by 266-283 

of  milk  by  ... 273 

micrococcus,  melitensis  in 17 

mode  of  infection  with  typhoid  bacilli 270 

municipal  supplies  infected 270,  276 

protection  of 281-282 

purification  of 282-283 

spirillum  cholera?  in 15 

sterilization  of  municipal 283 

storage  of 282 

Watercress,  typhoid  fever  caused  by 318-319 

Wells,  amount  of  typhoid  fever  due  to 272-274 

cholera  infection  from 275-276 

conditions  of  safety 274 

infection  from 266-267,  271-275 

protection  of 281 

Whooping  cough,  not  of  extra-corporal  origin 25 

Willard  State  Hospital,  diphtheria  in 102 

Wind  blowing  sewage  to  water  works  cause  of  typhoid  fever 270 

Wool,  anthrax  from 185 

spores  in 184-185 

Worms  derived  from  water 280 

Wounds,  infection  of ,  by  air 250-251 

Yellow  fever  an  endemic  disease 26 

and  bagging 171 

ballast 171 

cloth 171 

fomites 171-172,  334 

fomites,  experiments  in  Havana 203 

grain 171 

mattress 171 

merchandise 171 

mosquitoes 332-338 

oyster  buckets 171 

quarantine 336 

mosquito  destruction 337 

mosquito,  habits  of 335 

not  due  to  soil  infection 26 

from  water 279 

virus  filterable 333-334 


INDEX  399 

Page 

Yellow  fever  virus  in  blood •• ooooof 

Yellow  fever,  discovery  of  causation 332-334 

latent  period  in  outbreaks 333-334 

mild  and  atypical  cases 89 

preventive  measures 336-337 

quarantine  officers  take  the  temperature  of  passen- 
gers for  detection  of 89 

screening  of  cases _. 336-337 

success  of  mosquito  destruction 331,  335,  337-338 


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